Google JavaScript Style Guide
1 Introduction
This document serves as the complete definition of Google’s coding standards for source code in the JavaScript programming language. A JavaScript source file is described as being in Google Style if and only if it adheres to the rules herein.
Like other programming style guides, the issues covered span not only aesthetic issues of formatting, but other types of conventions or coding standards as well. However, this document focuses primarily on the hard-and-fast rules that we follow universally, and avoids giving advice that isn't clearly enforceable (whether by human or tool).
1.1 Terminology notes
In this document, unless otherwise clarified:
The term comment always refers to implementation comments. We do not use the phrase
documentation comments
, instead using the common term “JSDoc” for both human-readable text and machine-readable annotations within/** … */
.This Style Guide uses RFC 2119 terminology when using the phrases must, must not, should, should not, and may. The terms prefer and avoid correspond to should and should not, respectively. Imperative and declarative statements are prescriptive and correspond to must.
Other terminology notes
will appear occasionally throughout the document.
1.2 Guide notes
Example code in this document is non-normative. That is, while the examples are in Google Style, they may not illustrate the only stylish way to represent the code. Optional formatting choices made in examples must not be enforced as rules.
2 Source file basics
2.1 File name
File names must be all lowercase and may include underscores (_
) or dashes
(-
), but no additional punctuation. Follow the convention that your project
uses. Filenames’ extension must be .js
.
2.2 File encoding: UTF-8
Source files are encoded in UTF-8.
2.3 Special characters
2.3.1 Whitespace characters
Aside from the line terminator sequence, the ASCII horizontal space character (0x20) is the only whitespace character that appears anywhere in a source file. This implies that
All other whitespace characters in string literals are escaped, and
Tab characters are not used for indentation.
2.3.2 Special escape sequences
For any character that has a special escape sequence (\'
, \"
, \\
, \b
,
\f
, \n
, \r
, \t
, \v
), that sequence is used rather than the
corresponding numeric escape (e.g \x0a
, \u000a
, or \u{a}
). Legacy octal
escapes are never used.
2.3.3 Non-ASCII characters
For the remaining non-ASCII characters, either the actual Unicode character
(e.g. ∞
) or the equivalent hex or Unicode escape (e.g. \u221e
) is used,
depending only on which makes the code easier to read and understand.
Tip: In the Unicode escape case, and occasionally even when actual Unicode characters are used, an explanatory comment can be very helpful.
| Example | Discussion |
|---|---|
const units = 'μs';
| Best: perfectly clear even without a comment. |
const units = '\u03bcs'; // 'μs'
| Allowed, but there’s no reason to do this. |
const units = '\u03bcs'; // Greek letter mu, 's'
| Allowed, but awkward and prone to mistakes. |
const units = '\u03bcs';
| Poor: the reader has no idea what this is. |
return '\ufeff' + content; // byte order mark
| Good: use escapes for non-printable characters, and comment if necessary. |
Tip: Never make your code less readable simply out of fear that some programs might not handle non-ASCII characters properly. If that happens, those programs are broken and they must be fixed.
3 Source file structure
A source file consists of, in order:
- License or copyright information, if present
@fileoverview
JSDoc, if presentgoog.module
statementgoog.require
statements- The file’s implementation
Exactly one blank line separates each section that is present, except the file's implementation, which may be preceded by 1 or 2 blank lines.
3.1 License or copyright information, if present
If license or copyright information belongs in a file, it belongs here.
3.2 @fileoverview
JSDoc, if present
See ?? for formatting rules.
3.3 goog.module
statement
All files must declare exactly one goog.module
name on a single line: lines
containing a goog.module
declaration must not be wrapped, and are therefore an
exception to the 80-column limit.
The entire argument to goog.module is what defines a namespace. It is the package name (an identifier that reflects the fragment of the directory structure where the code lives) plus, optionally, the main class/enum/interface that it defines concatenated to the end.
Example
goog.module('search.urlHistory.UrlHistoryService');
3.3.1 Hierarchy
Module namespaces may never be named as a direct child of another module's namespace.
Illegal:
goog.module('foo.bar'); // 'foo.bar.qux' would be fine, though
goog.module('foo.bar.baz');
The directory hierarchy reflects the namespace hierarchy, so that deeper-nested children are subdirectories of higher-level parent directories. Note that this implies that owners of “parent” namespace groups are necessarily aware of all child namespaces, since they exist in the same directory.
3.3.2 goog.setTestOnly
The single goog.module
statement may optionally be followed by a call to
goog.setTestOnly().
3.3.3 goog.module.declareLegacyNamespace
The single goog.module
statement may optionally be followed by a call to
goog.module.declareLegacyNamespace();
. Avoid
goog.module.declareLegacyNamespace()
when possible.
Example:
goog.module('my.test.helpers');
goog.module.declareLegacyNamespace();
goog.setTestOnly();
goog.module.declareLegacyNamespace
exists to ease the transition from
traditional object hierarchy-based namespaces but comes with some naming
restrictions. As the child module name must be created after the parent
namespace, this name must not be a child or parent of any other
goog.module
(for example, goog.module('parent');
and
goog.module('parent.child');
cannot both exist safely, nor can
goog.module('parent');
and goog.module('parent.child.grandchild');
).
3.3.4 ES6 Modules
Do not use ES6 modules yet (i.e. the export
and import
keywords), as their
semantics are not yet finalized. Note that this policy will be revisited once
the semantics are fully-standard.
3.4 goog.require
statements
Imports are done with goog.require
statements, grouped together immediately
following the module declaration. Each goog.require
is assigned to a single
constant alias, or else destructured into several constant aliases. These
aliases are the only acceptable way to refer to the require
d dependency,
whether in code or in type annotations: the fully qualified name is never used
except as the argument to goog.require
. Alias names should match the final
dot-separated component of the imported module name when possible, though
additional components may be included (with appropriate casing such that the
alias' casing still correctly identifies its type) if necessary to
disambiguate, or if it significantly improves readability. goog.require
statements may not appear anywhere else in the file.
If a module is imported only for its side effects, the assignment may be omitted, but the fully qualified name may not appear anywhere else in the file. A comment is required to explain why this is needed and suppress a compiler warning.
The lines are sorted according to the following rules: All requires with a name
on the left hand side come first, sorted alphabetically by those names. Then
destructuring requires, again sorted by the names on the left hand side.
Finally, any goog.require
calls that are standalone (generally these are for
modules imported just for their side effects).
Tip: There’s no need to memorize this order and enforce it manually. You can rely on your IDE to report requires that are not sorted correctly.
If a long alias or module name would cause a line to exceed the 80-column limit, it must not be wrapped: goog.require lines are an exception to the 80-column limit.
Example:
const MyClass = goog.require('some.package.MyClass');
const NsMyClass = goog.require('other.ns.MyClass');
const googAsserts = goog.require('goog.asserts');
const testingAsserts = goog.require('goog.testing.asserts');
const than80columns = goog.require('pretend.this.is.longer.than80columns');
const {clear, forEach, map} = goog.require('goog.array');
/** @suppress {extraRequire} Initializes MyFramework. */
goog.require('my.framework.initialization');
Illegal:
const randomName = goog.require('something.else'); // name must match
const {clear, forEach, map} = // don't break lines
goog.require('goog.array');
function someFunction() {
const alias = goog.require('my.long.name.alias'); // must be at top level
// …
}
3.4.1 goog.forwardDeclare
goog.forwardDeclare
is not needed very often, but is a valuable tool to break
circular dependencies or to reference late loaded code. These statements are
grouped together and immediately follow any goog.require
statements. A
goog.forwardDeclare
statement must follow the same style rules as a
goog.require
statement.
3.5 The file’s implementation
The actual implementation follows after all dependency information is declared (separated by at least one blank line).
This may consist of any module-local declarations (constants, variables, classes, functions, etc), as well as any exported symbols.
4 Formatting
Terminology Note: block-like construct refers to the body of a class, function, method, or brace-delimited block of code. Note that, by ?? and ??, any array or object literal may optionally be treated as if it were a block-like construct.
Tip: Use clang-format
. The JavaScript community has invested effort to make
sure clang-format does the right thing
on JavaScript files. clang-format
has
integration with several popular
editors.
4.1 Braces
4.1.1 Braces are used for all control structures
Braces are required for all control structures (i.e. if
, else
, for
, do
,
while
, as well as any others), even if the body contains only a single
statement. The first statement of a non-empty block must begin on its own line.
Illegal:
if (someVeryLongCondition())
doSomething();
for (let i = 0; i < foo.length; i++) bar(foo[i]);
Exception: A simple if statement that can fit entirely on a single line with no wrapping (and that doesn’t have an else) may be kept on a single line with no braces when it improves readability. This is the only case in which a control structure may omit braces and newlines.
if (shortCondition()) return;
4.1.2 Nonempty blocks: K&R style
Braces follow the Kernighan and Ritchie style (Egyptian brackets
) for
nonempty blocks and block-like constructs:
- No line break before the opening brace.
- Line break after the opening brace.
- Line break before the closing brace.
- Line break after the closing brace if that brace terminates a statement or
the body of a function or class statement, or a class method. Specifically,
there is no line break after the brace if it is followed by
else
,catch
,while
, or a comma, semicolon, or right-parenthesis.
Example:
class InnerClass {
constructor() {}
/** @param {number} foo */
method(foo) {
if (condition(foo)) {
try {
// Note: this might fail.
something();
} catch (err) {
recover();
}
}
}
}
4.1.3 Empty blocks: may be concise
An empty block or block-like construct may be closed immediately after it is
opened, with no characters, space, or line break in between (i.e. {}
),
unless it is a part of a multi-block statement (one that directly contains
multiple blocks: if
/else
or try
/catch
/finally
).
Example:
function doNothing() {}
Illegal:
if (condition) {
// …
} else if (otherCondition) {} else {
// …
}
try {
// …
} catch (e) {}
4.2 Block indentation: +2 spaces
Each time a new block or block-like construct is opened, the indent increases by two spaces. When the block ends, the indent returns to the previous indent level. The indent level applies to both code and comments throughout the block. (See the example in ??).
4.2.1 Array literals: optionally block-like
Any array literal may optionally be formatted as if it were a “block-like construct.” For example, the following are all valid (not an exhaustive list):
const a = [
0,
1,
2,
];
const b =
[0, 1, 2];
const c = [0, 1, 2];
someMethod(foo, [
0, 1, 2,
], bar);
Other combinations are allowed, particularly when emphasizing semantic groupings between elements, but should not be used only to reduce the vertical size of larger arrays.
4.2.2 Object literals: optionally block-like
Any object literal may optionally be formatted as if it were a “block-like construct.” The same examples apply as ??. For example, the following are all valid (not an exhaustive list):
const a = {
a: 0,
b: 1,
};
const b =
{a: 0, b: 1};
const c = {a: 0, b: 1};
someMethod(foo, {
a: 0, b: 1,
}, bar);
4.2.3 Class literals
Class literals (whether declarations or expressions) are indented as blocks. Do
not add semicolons after methods, or after the closing brace of a class
declaration (statements—such as assignments—that contain class expressions
are still terminated with a semicolon). Use the extends
keyword, but not the
@extends
JSDoc annotation unless the class extends a templatized type.
Example:
class Foo {
constructor() {
/** @type {number} */
this.x = 42;
}
/** @return {number} */
method() {
return this.x;
}
}
Foo.Empty = class {};
/** @extends {Foo<string>} */
foo.Bar = class extends Foo {
/** @override */
method() {
return super.method() / 2;
}
};
/** @interface */
class Frobnicator {
/** @param {string} message */
frobnicate(message) {}
}
4.2.4 Function expressions
When declaring an anonymous function in the list of arguments for a function call, the body of the function is indented two spaces more than the preceding indentation depth.
Example:
prefix.something.reallyLongFunctionName('whatever', (a1, a2) => {
// Indent the function body +2 relative to indentation depth
// of the 'prefix' statement one line above.
if (a1.equals(a2)) {
someOtherLongFunctionName(a1);
} else {
andNowForSomethingCompletelyDifferent(a2.parrot);
}
});
some.reallyLongFunctionCall(arg1, arg2, arg3)
.thatsWrapped()
.then((result) => {
// Indent the function body +2 relative to the indentation depth
// of the '.then()' call.
if (result) {
result.use();
}
});
4.2.5 Switch statements
As with any other block, the contents of a switch block are indented +2.
After a switch label, a newline appears, and the indentation level is increased +2, exactly as if a block were being opened. An explicit block may be used if required by lexical scoping. The following switch label returns to the previous indentation level, as if a block had been closed.
A blank line is optional between a break
and the following case.
Example:
switch (animal) {
case Animal.BANDERSNATCH:
handleBandersnatch();
break;
case Animal.JABBERWOCK:
handleJabberwock();
break;
default:
throw new Error('Unknown animal');
}
4.3 Statements
4.3.1 One statement per line
Each statement is followed by a line-break.
4.3.2 Semicolons are required
Every statement must be terminated with a semicolon. Relying on automatic semicolon insertion is forbidden.
4.4 Column limit: 80
JavaScript code has a column limit of 80 characters. Except as noted below, any line that would exceed this limit must be line-wrapped, as explained in ??.
Exceptions:
- Lines where obeying the column limit is not possible (for example, a long URL in JSDoc or a shell command intended to be copied-and-pasted).
goog.module
andgoog.require
statements (see ?? and ??).
4.5 Line-wrapping
Terminology Note: Line-wrapping is defined as breaking a single expression into multiple lines.
There is no comprehensive, deterministic formula showing exactly how to line-wrap in every situation. Very often there are several valid ways to line-wrap the same piece of code.
Note: While the typical reason for line-wrapping is to avoid overflowing the column limit, even code that would in fact fit within the column limit may be line-wrapped at the author's discretion.
Tip: Extracting a method or local variable may solve the problem without the need to line-wrap.
4.5.1 Where to break
The prime directive of line-wrapping is: prefer to break at a higher syntactic level.
Preferred:
currentEstimate =
calc(currentEstimate + x * currentEstimate) /
2.0f;
Discouraged:
currentEstimate = calc(currentEstimate + x *
currentEstimate) / 2.0f;
In the preceding example, the syntactic levels from highest to lowest are as follows: assignment, division, function call, parameters, number constant.
Operators are wrapped as follows:
- When a line is broken at an operator the break comes after the symbol. (Note
that this is not the same practice used in Google style for Java.)
- This does not apply to the
dot
(.
), which is not actually an operator.
- This does not apply to the
- A method or constructor name stays attached to the open parenthesis (
(
) that follows it. - A comma (
,
) stays attached to the token that precedes it.
Note: The primary goal for line wrapping is to have clear code, not necessarily code that fits in the smallest number of lines.
4.5.2 Indent continuation lines at least +4 spaces
When line-wrapping, each line after the first (each continuation line) is indented at least +4 from the original line, unless it falls under the rules of block indentation.
When there are multiple continuation lines, indentation may be varied beyond +4 as appropriate. In general, continuation lines at a deeper syntactic level are indented by larger multiples of 4, and two lines use the same indentation level if and only if they begin with syntactically parallel elements.
?? addresses the discouraged practice of using a variable number of spaces to align certain tokens with previous lines.
4.6 Whitespace
4.6.1 Vertical whitespace
A single blank line appears:
- Between consecutive methods in a class or object literal
- Exception: A blank line between two consecutive properties definitions in an object literal (with no other code between them) is optional. Such blank lines are used as needed to create logical groupings of fields.
- Within method bodies, sparingly to create logical groupings of statements. Blank lines at the start or end of a function body are not allowed.
- Optionally before the first or after the last method in a class or object literal (neither encouraged nor discouraged).
- As required by other sections of this document (e.g. ??).
Multiple consecutive blank lines are permitted, but never required (nor encouraged).
4.6.2 Horizontal whitespace
Use of horizontal whitespace depends on location, and falls into three broad categories: leading (at the start of a line), trailing (at the end of a line), and internal. Leading whitespace (i.e., indentation) is addressed elsewhere. Trailing whitespace is forbidden.
Beyond where required by the language or other style rules, and apart from literals, comments, and JSDoc, a single internal ASCII space also appears in the following places only.
- Separating any reserved word (such as
if
,for
, orcatch
) from an open parenthesis ((
) that follows it on that line. - Separating any reserved word (such as
else
orcatch
) from a closing curly brace (}
) that precedes it on that line. - Before any open curly brace (
{
), with two exceptions:- Before an object literal that is the first argument of a function or the
first element in an array literal (e.g.
foo({a: [{c: d}]})
). - In a template expansion, as it is forbidden by the language
(e.g.
abc${1 + 2}def
).
- Before an object literal that is the first argument of a function or the
first element in an array literal (e.g.
- On both sides of any binary or ternary operator.
- After a comma (
,
) or semicolon (;
). Note that spaces are never allowed before these characters. - After the colon (
:
) in an object literal. - On both sides of the double slash (
//
) that begins an end-of-line comment. Here, multiple spaces are allowed, but not required. - After an open-JSDoc comment character and on both sides of close characters
(e.g. for short-form type declarations or casts:
this.foo = /** @type {number} */ (bar);
orfunction(/** string */ foo) {
).
4.6.3 Horizontal alignment: discouraged
Terminology Note: Horizontal alignment is the practice of adding a variable number of additional spaces in your code with the goal of making certain tokens appear directly below certain other tokens on previous lines.
This practice is permitted, but it is generally discouraged by Google Style. It is not even required to maintain horizontal alignment in places where it was already used.
Here is an example without alignment, followed by one with alignment. Both are allowed, but the latter is discouraged:
{
tiny: 42, // this is great
longer: 435, // this too
};
{
tiny: 42, // permitted, but future edits
longer: 435, // may leave it unaligned
};
Tip: Alignment can aid readability, but it creates problems for future
maintenance. Consider a future change that needs to touch just one line. This
change may leave the formerly-pleasing formatting mangled, and that is
allowed. More often it prompts the coder (perhaps you) to adjust whitespace on
nearby lines as well, possibly triggering a cascading series of
reformattings. That one-line change now has a blast radius.
This can at worst
result in pointless busywork, but at best it still corrupts version history
information, slows down reviewers and exacerbates merge conflicts.
4.6.4 Function arguments
Prefer to put all function arguments on the same line as the function name. If doing so would exceed the 80-column limit, the arguments must be line-wrapped in a readable way. To save space, you may wrap as close to 80 as possible, or put each argument on its own line to enhance readability. Indentation should be four spaces. Aligning to the parenthesis is allowed, but discouraged. Below are the most common patterns for argument wrapping:
// Arguments start on a new line, indented four spaces. Preferred when the
// arguments don't fit on the same line with the function name (or the keyword
// "function") but fit entirely on the second line. Works with very long
// function names, survives renaming without reindenting, low on space.
doSomething(
descriptiveArgumentOne, descriptiveArgumentTwo, descriptiveArgumentThree) {
// …
}
// If the argument list is longer, wrap at 80. Uses less vertical space,
// but violates the rectangle rule and is thus not recommended.
doSomething(veryDescriptiveArgumentNumberOne, veryDescriptiveArgumentTwo,
tableModelEventHandlerProxy, artichokeDescriptorAdapterIterator) {
// …
}
// Four-space, one argument per line. Works with long function names,
// survives renaming, and emphasizes each argument.
doSomething(
veryDescriptiveArgumentNumberOne,
veryDescriptiveArgumentTwo,
tableModelEventHandlerProxy,
artichokeDescriptorAdapterIterator) {
// …
}
4.7 Grouping parentheses: recommended
Optional grouping parentheses are omitted only when the author and reviewer agree that there is no reasonable chance that the code will be misinterpreted without them, nor would they have made the code easier to read. It is not reasonable to assume that every reader has the entire operator precedence table memorized.
Do not use unnecessary parentheses around the entire expression following
delete
, typeof
, void
, return
, throw
, case
, in
, of
, or yield
.
Parentheses are required for type casts: /** @type {!Foo} */ (foo)
.
4.8 Comments
This section addresses implementation comments. JSDoc is addressed separately in ??.
4.8.1 Block comment style
Block comments are indented at the same level as the surrounding code. They may
be in /* … */
or //
-style. For multi-line /* … */
comments, subsequent
lines must start with * aligned with the *
on the previous line, to make
comments obvious with no extra context. “Parameter name” comments should appear
after values whenever the value and method name do not sufficiently convey the
meaning.
/*
* This is
* okay.
*/
// And so
// is this.
/* This is fine, too. */
someFunction(obviousParam, true /* shouldRender */, 'hello' /* name */);
Comments are not enclosed in boxes drawn with asterisks or other characters.
Do not use JSDoc (/** … */
) for any of the above implementation comments.
5 Language features
JavaScript includes many dubious (and even dangerous) features. This section delineates which features may or may not be used, and any additional constraints on their use.
5.1 Local variable declarations
5.1.1 Use const
and let
Declare all local variables with either const
or let
. Use const by default,
unless a variable needs to be reassigned. The var
keyword must not be used.
5.1.2 One variable per declaration
Every local variable declaration declares only one variable: declarations such
as let a = 1, b = 2;
are not used.
5.1.3 Declared when needed, initialized as soon as possible
Local variables are not habitually declared at the start of their containing block or block-like construct. Instead, local variables are declared close to the point they are first used (within reason), to minimize their scope.
5.1.4 Declare types as needed
JSDoc type annotations may be added either on the line above the declaration, or else inline before the variable name.
Example:
const /** !Array<number> */ data = [];
/** @type {!Array<number>} */
const data = [];
Tip: There are many cases where the compiler can infer a templatized type but
not its parameters. This is particularly the case when the initializing literal
or constructor call does not include any values of the template parameter type
(e.g., empty arrays, objects, Map
s, or Set
s), or if the variable is modified
in a closure. Local variable type annotations are particularly helpful in these
cases since otherwise the compiler will infer the template parameter as unknown.
5.2 Array literals
5.2.1 Use trailing commas
Include a trailing comma whenever there is a line break between the final element and the closing bracket.
Example:
const values = [
'first value',
'second value',
];
5.2.2 Do not use the variadic Array
constructor
The constructor is error-prone if arguments are added or removed. Use a literal instead.
Illegal:
const a1 = new Array(x1, x2, x3);
const a2 = new Array(x1, x2);
const a3 = new Array(x1);
const a4 = new Array();
This works as expected except for the third case: if x1
is a whole number then
a3
is an array of size x1
where all elements are undefined
. If x1
is any
other number, then an exception will be thrown, and if it is anything else then
it will be a single-element array.
Instead, write
const a1 = [x1, x2, x3];
const a2 = [x1, x2];
const a3 = [x1];
const a4 = [];
Explicitly allocating an array of a given length using new Array(length)
is
allowed when appropriate.
5.2.3 Non-numeric properties
Do not define or use non-numeric properties on an array (other than
length
). Use a Map
(or Object
) instead.
5.2.4 Destructuring
Array literals may be used on the left-hand side of an assignment to perform
destructuring (such as when unpacking multiple values from a single array or
iterable). A final rest
element may be included (with no space between the
...
and the variable name). Elements should be omitted if they are unused.
const [a, b, c, ...rest] = generateResults();
let [, b,, d] = someArray;
Destructuring may also be used for function parameters (note that a parameter
name is required but ignored). Always specify []
as the default value if a
destructured array parameter is optional, and provide default values on the left
hand side:
/** @param {!Array<number>=} param1 */
function optionalDestructuring([a = 4, b = 2] = []) { … };
Illegal:
function badDestructuring([a, b] = [4, 2]) { … };
Tip: For (un)packing multiple values into a function’s parameter or return, prefer object destructuring to array destructuring when possible, as it allows naming the individual elements and specifying a different type for each.*
5.2.5 Spread operator
Array literals may include the spread operator (...
) to flatten elements out
of one or more other iterables. The spread operator should be used instead of
more awkward constructs with Array.prototype
. There is no space after the
...
.
Example:
[...foo] // preferred over Array.prototype.slice.call(foo)
[...foo, ...bar] // preferred over foo.concat(bar)
5.3 Object literals
5.3.1 Use trailing commas
Include a trailing comma whenever there is a line break between the final property and the closing brace.
5.3.2 Do not use the Object
constructor
While Object
does not have the same problems as Array
, it is still
disallowed for consistency. Use an object literal ({}
or {a: 0, b: 1, c: 2}
)
instead.
5.3.3 Do not mix quoted and unquoted keys
Object literals may represent either structs (with unquoted keys and/or symbols) or dicts (with quoted and/or computed keys). Do not mix these key types in a single object literal.
Illegal:
{
a: 42, // struct-style unquoted key
'b': 43, // dict-style quoted key
}
5.3.4 Computed property names
Computed property names (e.g., {['key' + foo()]: 42}
) are allowed, and are
considered dict-style (quoted) keys (i.e., must not be mixed with non-quoted
keys) unless the computed property is a symbol (e.g., [Symbol.iterator]
).
Enum values may also be used for computed keys, but should not be mixed with
non-enum keys in the same literal.
5.3.5 Method shorthand
Methods can be defined on object literals using the method shorthand ({method()
{… }}
) in place of a colon immediately followed by a function
or arrow
function literal.
Example:
return {
stuff: 'candy',
method() {
return this.stuff; // Returns 'candy'
},
};
Note that this
in a method shorthand or function
refers to the object
literal itself whereas this
in an arrow function refers to the scope outside
the object literal.
Example:
class {
getObjectLiteral() {
this.stuff = 'fruit';
return {
stuff: 'candy',
method: () => this.stuff, // Returns 'fruit'
};
}
}
5.3.6 Shorthand properties
Shorthand properties are allowed on object literals.
Example:
const foo = 1;
const bar = 2;
const obj = {
foo,
bar,
method() { return this.foo + this.bar; },
};
assertEquals(3, obj.method());
5.3.7 Destructuring
Object destructuring patterns may be used on the left-hand side of an assignment to perform destructuring and unpack multiple values from a single object.
Destructured objects may also be used as function parameters, but should be kept
as simple as possible: a single level of unquoted shorthand properties. Deeper
levels of nesting and computed properties may not be used in parameter
destructuring. Specify any default values in the left-hand-side of the
destructured parameter ({str = 'some default'} = {}
, rather than {str} = {str: 'some default'}
), and if a destructured
object is itself optional, it must default to {}
. The JSDoc for the
destructured parameter may be given any name (the name is unused but is required
by the compiler).
Example:
/**
* @param {string} ordinary
* @param {{num: (number|undefined), str: (string|undefined)}=} param1
* num: The number of times to do something.
* str: A string to do stuff to.
*/
function destructured(ordinary, {num, str = 'some default'} = {})
Illegal:
/** @param {{x: {num: (number|undefined), str: (string|undefined)}}} param1 */
function nestedTooDeeply({x: {num, str}}) {};
/** @param {{num: (number|undefined), str: (string|undefined)}=} param1 */
function nonShorthandProperty({num: a, str: b} = {}) {};
/** @param {{a: number, b: number}} param1 */
function computedKey({a, b, [a + b]: c}) {};
/** @param {{a: number, b: string}=} param1 */
function nontrivialDefault({a, b} = {a: 2, b: 4}) {};
Destructuring may also be used for goog.require
statements, and in this case
must not be wrapped: the entire statement occupies one line, regardless of how
long it is (see ??).
5.3.8 Enums
Enumerations are defined by adding the @enum
annotation to an object literal.
Additional properties may not be added to an enum after it is defined. Enums
must be constant, and all enum values must be deeply immutable.
/**
* Supported temperature scales.
* @enum {string}
*/
const TemperatureScale = {
CELSIUS: 'celsius',
FAHRENHEIT: 'fahrenheit',
};
/**
* An enum with two options.
* @enum {number}
*/
const Option = {
/** The option used shall have been the first. */
FIRST_OPTION: 1,
/** The second among two options. */
SECOND_OPTION: 2,
};
5.4 Classes
5.4.1 Constructors
Constructors are optional for concrete classes. Subclass constructors must call
super()
before setting any fields or otherwise accessing this
. Interfaces
must not define a constructor.
5.4.2 Fields
Set all of a concrete object’s fields (i.e. all properties other than methods)
in the constructor. Annotate fields that are never reassigned with @const
(these need not be deeply immutable). Private fields must be annotated with
@private
and their names must end with a trailing underscore. Fields are never
set on a concrete class' prototype
.
Example:
class Foo {
constructor() {
/** @private @const {!Bar} */
this.bar_ = computeBar();
}
}
Tip: Properties should never be added to or removed from an instance after the
constructor is finished, since it significantly hinders VMs’ ability to
optimize. If necessary, fields that are initialized later should be explicitly
set to undefined
in the constructor to prevent later shape changes. Adding
@struct
to an object will check that undeclared properties are not
added/accessed. Classes have this added by default.
5.4.3 Computed properties
Computed properties may only be used in classes when the property is a
symbol. Dict-style properties (that is, quoted or computed non-symbol keys, as
defined in ??) are not allowed. A
[Symbol.iterator]
method should be defined for any classes that are logically
iterable. Beyond this, Symbol
should be used sparingly.
Tip: be careful of using any other built-in symbols (e.g., Symbol.isConcatSpreadable
) as they are not polyfilled by the compiler and will therefore not work in older browsers.
5.4.4 Static methods
Where it does not interfere with readability, prefer module-local functions over private static methods.
Static methods should only be called on the base class itself. Static methods
should not be called on variables containing a dynamic instance that may be
either the constructor or a subclass constructor (and must be defined with
@nocollapse
if this is done), and must not be called directly on a subclass
that doesn’t define the method itself.
Illegal:
class Base { /** @nocollapse */ static foo() {} }
class Sub extends Base {}
function callFoo(cls) { cls.foo(); } // discouraged: don't call static methods dynamically
Sub.foo(); // illegal: don't call static methods on subclasses that don't define it themselves
5.4.5 Old-style class declarations
While ES6 classes are preferred, there are cases where ES6 classes may not be feasible. For example:
If there exist or will exist subclasses, including frameworks that create subclasses, that cannot be immediately changed to use ES6 class syntax. If such a class were to use ES6 syntax, all downstream subclasses not using ES6 class syntax would need to be modified.
Frameworks that require a known
this
value before calling the superclass constructor, since constructors with ES6 super classes do not have access to the instancethis
value until the call tosuper
returns.
In all other ways the style guide still applies to this code: let
, const
,
default parameters, rest, and arrow functions should all be used when
appropriate.
goog.defineClass
allows for a class-like definition similar to ES6 class
syntax:
let C = goog.defineClass(S, {
/**
* @param {string} value
*/
constructor(value) {
S.call(this, 2);
/** @const */
this.prop = value;
},
/**
* @param {string} param
* @return {number}
*/
method(param) {
return 0;
},
});
Alternatively, while goog.defineClass
should be preferred for all new code,
more traditional syntax is also allowed.
/**
* @constructor @extends {S}
* @param {string} value
*/
function C(value) {
S.call(this, 2);
/** @const */
this.prop = value;
}
goog.inherits(C, S);
/**
* @param {string} param
* @return {number}
*/
C.prototype.method = function(param) {
return 0;
};
Per-instance properties should be defined in the constructor after the call to the super class constructor, if there is a super class. Methods should be defined on the prototype of the constructor.
Defining constructor prototype hierarchies correctly is harder than it first appears! For that reason, it is best to use goog.inherits
from the Closure Library .
5.4.6 Do not manipulate prototype
s directly
The class
keyword allows clearer and more readable class definitions than
defining prototype
properties. Ordinary implementation code has no business
manipulating these objects, though they are still useful for defining @record
interfaces and classes as defined in ??. Mixins
and modifying the prototypes of builtin objects are
explicitly forbidden.
Exception: Framework code (such as Polymer, or Angular) may need to use prototype
s, and should not
resort to even-worse workarounds to avoid doing so.
Exception: Defining fields in interfaces (see ??).
5.4.7 Getters and Setters
Do not use JavaScript getter and setter properties. They are potentially surprising and difficult to reason about, and have limited support in the compiler. Provide ordinary methods instead.
Exception: when working with data binding frameworks (such as Angular and
Polymer), getters and setters may be used sparingly. Note, however, that
compiler support is limited. When they are used, they must be defined either
with get foo()
and set foo(value)
in the class or object literal, or if that
is not possible, with Object.defineProperties
. Do not use
Object.defineProperty
, which interferes with property renaming. Getters
must not change observable state.
Illegal:
class Foo {
get next() { return this.nextId++; }
}
5.4.8 Overriding toString
The toString
method may be overridden, but must always succeed and never have
visible side effects.
Tip: Beware, in particular, of calling other methods from toString, since exceptional conditions could lead to infinite loops.
5.4.9 Interfaces
Interfaces may be declared with @interface
or @record
. Interfaces declared
with @record
can be explicitly (i.e. via @implements
) or implicitly
implemented by a class or object literal.
All non-static method bodies on an interface must be empty blocks. Fields must
be defined after the interface body as stubs on the prototype
.
Example:
/**
* Something that can frobnicate.
* @record
*/
class Frobnicator {
/**
* Performs the frobnication according to the given strategy.
* @param {!FrobnicationStrategy} strategy
*/
frobnicate(strategy) {}
}
/** @type {number} The number of attempts before giving up. */
Frobnicator.prototype.attempts;
5.5 Functions
5.5.1 Top-level functions
Exported functions may be defined directly on the exports
object, or else
declared locally and exported separately. Non-exported functions are encouraged
and should not be declared @private
.
Examples:
/** @return {number} */
function helperFunction() {
return 42;
}
/** @return {number} */
function exportedFunction() {
return helperFunction() * 2;
}
/**
* @param {string} arg
* @return {number}
*/
function anotherExportedFunction(arg) {
return helperFunction() / arg.length;
}
/** @const */
exports = {exportedFunction, anotherExportedFunction};
/** @param {string} arg */
exports.foo = (arg) => {
// do some stuff ...
};
5.5.2 Nested functions and closures
Functions may contain nested function definitions. If it is useful to give the
function a name, it should be assigned to a local const
.
5.5.3 Arrow functions
Arrow functions provide a concise syntax and fix a number of difficulties with
this
. Prefer arrow functions over the function
keyword, particularly for
nested functions (but see ??).
Prefer using arrow functions over f.bind(this)
, and especially over
goog.bind(f, this)
. Avoid writing const self = this
. Arrow functions are
particularly useful for callbacks, which sometimes pass unexpected additional
arguments.
The right-hand side of the arrow may be a single expression or a block. Parentheses around the arguments are optional if there is only a single non-destructured argument.
Tip: It is a good practice to use parentheses even for single-argument arrows, since the code may still parse reasonably (but incorrectly) if the parentheses are forgotten when an additional argument is added.
5.5.4 Generators
Generators enable a number of useful abstractions and may be used as needed.
When defining generator functions, attach the *
to the function
keyword when
present, and separate it with a space from the name of the function. When using
delegating yields, attach the *
to the yield
keyword.
Example:
/** @return {!Iterator<number>} */
function* gen1() {
yield 42;
}
/** @return {!Iterator<number>} */
const gen2 = function*() {
yield* gen1();
}
class SomeClass {
/** @return {!Iterator<number>} */
* gen() {
yield 42;
}
}
5.5.5 Parameters
Function parameters must be typed with JSDoc annotations in the JSDoc preceding
the function’s definition, except in the case of same-signature @override
s,
where all types are omitted.
Parameter types may be specified inline, immediately before the parameter name
(as in (/** number */ foo, /** string */ bar) => foo + bar
). Inline and
@param
type annotations must not be mixed in the same function definition.
<IP_ADDRESS> Default parameters
Optional parameters are permitted using the equals operator in the parameter
list. Optional parameters must include spaces on both sides of the equals
operator, be named exactly like required parameters (i.e., not prefixed with
opt_
), use the =
suffix in their JSDoc type, come after required parameters,
and not use initializers that produce observable side effects. All optional
parameters must have a default value in the function declaration, even if that
value is undefined
.
Example:
/**
* @param {string} required This parameter is always needed.
* @param {string=} optional This parameter can be omitted.
* @param {!Node=} node Another optional parameter.
*/
function maybeDoSomething(required, optional = '', node = undefined) {}
Use default parameters sparingly. Prefer destructuring (as in ??) to create readable APIs when there are more than a small handful of optional parameters that do not have a natural order.
Note: Unlike Python's default parameters, it is okay to use initializers that
return new mutable objects (such as {}
or []
) because the initializer is
evaluated each time the default value is used, so a single object won't be
shared across invocations.
Tip: While arbitrary expressions including function calls may be used as initializers, these should be kept as simple as possible. Avoid initializers that expose shared mutable state, as that can easily introduce unintended coupling between function calls.
<IP_ADDRESS> Rest parameters
Use a rest parameter instead of accessing arguments
. Rest parameters are
typed with a ...
prefix in their JSDoc. The rest parameter must be the last
parameter in the list. There is no space between the ...
and the parameter
name. Do not name the rest parameter var_args
. Never name a local variable or
parameter arguments
, which confusingly shadows the built-in name.
Example:
/**
* @param {!Array<string>} array This is an ordinary parameter.
* @param {...number} numbers The remainder of arguments are all numbers.
*/
function variadic(array, ...numbers) {}
5.5.6 Returns
Function return types must be specified in the JSDoc directly above the function
definition, except in the case of same-signature @override
s where all types
are omitted.
5.5.7 Generics
Declare generic functions and methods when necessary with @template TYPE
in
the JSDoc above the class definition.
5.5.8 Spread operator
Function calls may use the spread operator (...
). Prefer the spread operator
to Function.prototype.apply
when an array or iterable is unpacked into
multiple parameters of a variadic function. There is no space after the ...
.
Example:
function myFunction(...elements) {}
myFunction(...array, ...iterable, ...generator());
5.6 String literals
5.6.1 Use single quotes
Ordinary string literals are delimited with single quotes ('
), rather than
double quotes ("
).
Tip: if a string contains a single quote character, consider using a template string to avoid having to escape the quote.
Ordinary string literals may not span multiple lines.
5.6.2 Template strings
Use template strings (delimited with `
) over complex string
concatenation, particularly if multiple string literals are involved. Template
strings may span multiple lines.
If a template string spans multiple lines, it does not need to follow the indentation of the enclosing block, though it may if the added whitespace does not matter.
Example:
function arithmetic(a, b) {
return `Here is a table of arithmetic operations:
${a} + ${b} = ${a + b}
${a} - ${b} = ${a - b}
${a} * ${b} = ${a * b}
${a} / ${b} = ${a / b}`;
}
5.6.3 No line continuations
Do not use line continuations (that is, ending a line inside a string literal with a backslash) in either ordinary or template string literals. Even though ES5 allows this, it can lead to tricky errors if any trailing whitespace comes after the slash, and is less obvious to readers.
Illegal:
const longString = 'This is a very long string that far exceeds the 80 \
column limit. It unfortunately contains long stretches of spaces due \
to how the continued lines are indented.';
Instead, write
const longString = 'This is a very long string that far exceeds the 80 ' +
'column limit. It does not contain long stretches of spaces since ' +
'the concatenated strings are cleaner.';
5.7 Number literals
Numbers may be specified in decimal, hex, octal, or binary. Use exactly 0x
,
0o
, and 0b
prefixes, with lowercase letters, for hex, octal, and binary,
respectively. Never include a leading zero unless it is immediately followed by
x
, o
, or b
.
5.8 Control structures
5.8.1 For loops
With ES6, the language now has three different kinds of for
loops. All may be
used, though for
-of
loops should be preferred when possible.
for
-in
loops may only be used on dict-style objects (see
??), and should not be used to iterate over an
array. Object.prototype.hasOwnProperty
should be used in for
-in
loops to
exclude unwanted prototype properties. Prefer for
-of
and Object.keys
over
for
-in
when possible.
5.8.2 Exceptions
Exceptions are an important part of the language and should be used whenever
exceptional cases occur. Always throw Error
s or subclasses of Error
: never
throw string literals or other objects. Always use new
when constructing an
Error
.
Custom exceptions provide a great way to convey additional error information
from functions. They should be defined and used wherever the native Error
type is insufficient.
Prefer throwing exceptions over ad-hoc error-handling approaches (such as passing an error container reference type, or returning an object with an error property).
<IP_ADDRESS> Empty catch blocks
It is very rarely correct to do nothing in response to a caught exception. When it truly is appropriate to take no action whatsoever in a catch block, the reason this is justified is explained in a comment.
try {
return handleNumericResponse(response);
} catch (ok) {
// it's not numeric; that's fine, just continue
}
return handleTextResponse(response);
Illegal:
try {
shouldFail();
fail('expected an error');
}
catch (expected) {}
Tip: Unlike in some other languages, patterns like the above simply don’t work
since this will catch the error thrown by fail
. Use assertThrows()
instead.
5.8.3 Switch statements
Terminology Note: Inside the braces of a switch block are one or more statement groups. Each statement group consists of one or more switch labels (either case FOO:
or default:
), followed by one or more statements.
<IP_ADDRESS> Fall-through: commented
Within a switch block, each statement group either terminates abruptly (with a
break
, return
or throw
n exception), or is marked with a comment to
indicate that execution will or might continue into the next statement
group. Any comment that communicates the idea of fall-through is sufficient
(typically // fall through
). This special comment is not required in the last
statement group of the switch block.
Example:
switch (input) {
case 1:
case 2:
prepareOneOrTwo();
// fall through
case 3:
handleOneTwoOrThree();
break;
default:
handleLargeNumber(input);
}
<IP_ADDRESS> The default
case is present
Each switch statement includes a default
statement group, even if it contains
no code.
5.9 this
Only use this
in class constructors and methods, or in arrow functions defined
within class constructors and methods. Any other uses of this
must have an
explicit @this
declared in the immediately-enclosing function’s JSDoc.
Never use this
to refer to the global object, the context of an eval
, the
target of an event, or unnecessarily call()
ed or apply()
ed functions.
5.10 Disallowed features
5.10.1 with
Do not use the with
keyword. It makes your code harder to understand and has
been banned in strict mode since ES5.
5.10.2 Dynamic code evaluation
Do not use eval
or the Function(...string)
constructor (except for code
loaders). These features are potentially dangerous and simply do not work in
CSP environments.
5.10.3 Automatic semicolon insertion
Always terminate statements with semicolons (except function and class declarations, as noted above).
5.10.4 Non-standard features
Do not use non-standard features. This includes old features that have been
removed (e.g., WeakMap.clear
), new features that are not yet standardized
(e.g., the current TC39 working draft, proposals at any stage, or proposed but
not-yet-complete web standards), or proprietary features that are only
implemented in some browsers. Use only features defined in the current ECMA-262
or WHATWG standards. (Note that projects writing against specific APIs, such as
Chrome extensions or Node.js, can obviously use those APIs). Non-standard
language “extensions” (such as those provided by some external transpilers) are
forbidden.
5.10.5 Wrapper objects for primitive types
Never use new
on the primitive object wrappers (Boolean
, Number
, String
,
Symbol
), nor include them in type annotations.
Illegal:
const /** Boolean */ x = new Boolean(false);
if (x) alert(typeof x); // alerts 'object' - WAT?
The wrappers may be called as functions for coercing (which is preferred over
using +
or concatenating the empty string) or creating symbols.
Example:
const /** boolean */ x = Boolean(0);
if (!x) alert(typeof x); // alerts 'boolean', as expected
5.10.6 Modifying builtin objects
Never modify builtin types, either by adding methods to their constructors or to their prototypes. Avoid depending on libraries that do this. Note that the JSCompiler’s runtime library will provide standards-compliant polyfills where possible; nothing else may modify builtin objects.
Do not add symbols to the global object unless absolutely necessary (e.g. required by a third-party API).
6 Naming
6.1 Rules common to all identifiers
Identifiers use only ASCII letters and digits, and, in a small number of cases noted below, underscores and very rarely (when required by frameworks like Angular) dollar signs.
Give as descriptive a name as possible, within reason. Do not worry about saving horizontal space as it is far more important to make your code immediately understandable by a new reader. Do not use abbreviations that are ambiguous or unfamiliar to readers outside your project, and do not abbreviate by deleting letters within a word.
priceCountReader // No abbreviation.
numErrors // "num" is a widespread convention.
numDnsConnections // Most people know what "DNS" stands for.
Illegal:
n // Meaningless.
nErr // Ambiguous abbreviation.
nCompConns // Ambiguous abbreviation.
wgcConnections // Only your group knows what this stands for.
pcReader // Lots of things can be abbreviated "pc".
cstmrId // Deletes internal letters.
kSecondsPerDay // Do not use Hungarian notation.
6.2 Rules by identifier type
6.2.1 Package names
Package names are all lowerCamelCase
. For example,
my.exampleCode.deepSpace
, but not my.examplecode.deepspace
or my.example_code.deep_space
.
6.2.2 Class names
Class, interface, record, and typedef names are written in UpperCamelCase
.
Unexported classes are simply locals: they are not marked @private
and
therefore are not named with a trailing underscore.
Type names are typically nouns or noun phrases. For example, Request
,
ImmutableList
, or VisibilityMode
. Additionally, interface names may
sometimes be adjectives or adjective phrases instead (for example, Readable
).
6.2.3 Method names
Method names are written in lowerCamelCase
. Private methods’ names must end
with a trailing underscore.
Method names are typically verbs or verb phrases. For example, sendMessage
or
stop_
. Getter and setter methods for properties are never required, but if
they are used they should be named getFoo
(or optionally isFoo
or hasFoo
for booleans), or setFoo(value)
for setters.
Underscores may also appear in JsUnit test method names to separate logical
components of the name. One typical pattern is test<MethodUnderTest>_<state>
,
for example testPop_emptyStack
. There is no One Correct Way to name test
methods.
6.2.4 Enum names
Enum names are written in UpperCamelCase
, similar to classes, and should
generally be singular nouns. Individual items within the enum are named in
CONSTANT_CASE
.
6.2.5 Constant names
Constant names use CONSTANT_CASE
: all uppercase letters, with words separated
by underscores. There is no reason for a constant to be named with a trailing
underscore, since private static properties can be replaced by (implicitly
private) module locals.
<IP_ADDRESS> Definition of “constant”
Every constant is a @const
static property or a module-local const
declaration, but not all @const
static properties and module-local const
s
are constants. Before choosing constant case, consider whether the field really
feels like a deeply immutable constant. For example, if any of that instance's
observable state can change, it is almost certainly not a constant. Merely
intending to never mutate the object is generally not enough.
Examples:
// Constants
const NUMBER = 5;
/** @const */ exports.NAMES = ImmutableList.of('Ed', 'Ann');
/** @enum */ exports.SomeEnum = { ENUM_CONSTANT: 'value' };
// Not constants
let letVariable = 'non-const';
class MyClass { constructor() { /** @const */ this.nonStatic = 'non-static'; } };
/** @type {string} */ MyClass.staticButMutable = 'not @const, can be reassigned';
const /** Set<String> */ mutableCollection = new Set();
const /** ImmutableSet<SomeMutableType> */ mutableElements = ImmutableSet.of(mutable);
const Foo = goog.require('my.Foo'); // mirrors imported name
const logger = log.getLogger('loggers.are.not.immutable');
Constants’ names are typically nouns or noun phrases.
<IP_ADDRESS> Local aliases
Local aliases should be used whenever they improve readability over
fully-qualified names. Follow the same rules as goog.require
s
(??), maintaining the last part of the aliased name.
Aliases may also be used within functions. Aliases must be const
.
Examples:
const staticHelper = importedNamespace.staticHelper;
const CONSTANT_NAME = ImportedClass.CONSTANT_NAME;
const {assert, assertInstanceof} = asserts;
6.2.6 Non-constant field names
Non-constant field names (static or otherwise) are written in lowerCamelCase
,
with a trailing underscore for private fields.
These names are typically nouns or noun phrases. For example, computedValues
or index_
.
6.2.7 Parameter names
Parameter names are written in lowerCamelCase
. Note that this applies even if
the parameter expects a constructor.
One-character parameter names should not be used in public methods.
Exception: When required by a third-party framework, parameter names may
begin with a $
. This exception does not apply to any other identifiers
(e.g. local variables or properties).
6.2.8 Local variable names
Local variable names are written in lowerCamelCase
, except for module-local
(top-level) constants, as described above. Constants in function scopes are
still named in lowerCamelCase
. Note that lowerCamelCase applies even if the
variable holds a constructor.
6.2.9 Template parameter names
Template parameter names should be concise, single-word or single-letter
identifiers, and must be all-caps, such as TYPE
or THIS
.
6.3 Camel case: defined
Sometimes there is more than one reasonable way to convert an English phrase
into camel case, such as when acronyms or unusual constructs like IPv6
or
iOS
are present. To improve predictability, Google Style specifies the
following (nearly) deterministic scheme.
Beginning with the prose form of the name:
- Convert the phrase to plain ASCII and remove any apostrophes. For example,
Müller's algorithm
might becomeMuellers algorithm
. - Divide this result into words, splitting on spaces and any remaining
punctuation (typically hyphens).
- Recommended: if any word already has a conventional camel case
appearance in common usage, split this into its constituent parts (e.g.,
AdWords
becomesad words
). Note that a word such asiOS
is not really in camel case per se; it defies any convention, so this recommendation does not apply.
- Recommended: if any word already has a conventional camel case
appearance in common usage, split this into its constituent parts (e.g.,
- Now lowercase everything (including acronyms), then uppercase only the first
character of:
- … each word, to yield upper camel case, or
- … each word except the first, to yield lower camel case
- Finally, join all the words into a single identifier.
Note that the casing of the original words is almost entirely disregarded.
Examples:
| Prose form | Correct | Incorrect |
|---|---|---|
XML HTTP request |
XmlHttpRequest | XMLHTTPRequest |
new customer ID |
newCustomerId | newCustomerID |
inner stopwatch |
innerStopwatch | innerStopWatch |
supports IPv6 on iOS? |
supportsIpv6OnIos | supportsIPv6OnIOS |
YouTube importer |
YouTubeImporter | YoutubeImporter* |
*Acceptable, but not recommended.
Note: Some words are ambiguously hyphenated in the English language: for example nonempty
and non-empty
are both correct, so the method names checkNonempty and checkNonEmpty are likewise both correct.
7 JSDoc
JSDoc is used on all classes, fields, and methods.
7.1 General form
The basic formatting of JSDoc blocks is as seen in this example:
/**
* Multiple lines of JSDoc text are written here,
* wrapped normally.
* @param {number} arg A number to do something to.
*/
function doSomething(arg) { … }
or in this single-line example:
/** @const @private {!Foo} A short bit of JSDoc. */
this.foo_ = foo;
If a single-line comment overflows into multiple lines, it must use the
multi-line style with /**
and */
on their own lines.
Many tools extract metadata from JSDoc comments to perform code validation and optimization. As such, these comments must be well-formed.
7.2 Markdown
JSDoc is written in Markdown, though it may include HTML when necessary.
Note that tools that automatically extract JSDoc (e.g. JsDossier) will often ignore plain text formatting, so if you did this:
/**
* Computes weight based on three factors:
* items sent
* items received
* last timestamp
*/
it would come out like this:
Computes weight based on three factors: items sent items received last timestamp
Instead, write a Markdown list:
/**
* Computes weight based on three factors:
* - items sent
* - items received
* - last timestamp
*/
7.3 JSDoc tags
Google style allows a subset of JSDoc tags. See ?? for the complete list. Most tags must occupy their own line, with the tag at the beginning of the line.
Illegal:
/**
* The "param" tag must occupy its own line and may not be combined.
* @param {number} left @param {number} right
*/
function add(left, right) { ... }
Simple tags that do not require any additional data (such as @private
,
@const
, @final
, @export
) may be combined onto the same line, along with an
optional type when appropriate.
/**
* Place more complex annotations (like "implements" and "template")
* on their own lines. Multiple simple tags (like "export" and "final")
* may be combined in one line.
* @export @final
* @implements {Iterable<TYPE>}
* @template TYPE
*/
class MyClass {
/**
* @param {!ObjType} obj Some object.
* @param {number=} num An optional number.
*/
constructor(obj, num = 42) {
/** @private @const {!Array<!ObjType|number>} */
this.data_ = [obj, num];
}
}
There is no hard rule for when to combine tags, or in which order, but be consistent.
For general information about annotating types in JavaScript see Annotating JavaScript for the Closure Compiler and Types in the Closure Type System.
7.4 Line wrapping
Line-wrapped block tags are indented four spaces. Wrapped description text may be lined up with the description on previous lines, but this horizontal alignment is discouraged.
/**
* Illustrates line wrapping for long param/return descriptions.
* @param {string} foo This is a param with a description too long to fit in
* one line.
* @return {number} This returns something that has a description too long to
* fit in one line.
*/
exports.method = function(foo) {
return 5;
};
Do not indent when wrapping a @fileoverview
description.
7.5 Top/file-level comments
A file may have a top-level file overview. A copyright notice , author information, and default visibility level are optional. File overviews are generally recommended whenever a file consists of more than a single class definition. The top level comment is designed to orient readers unfamiliar with the code to what is in this file. If present, it may provide a description of the file's contents and any dependencies or compatibility information. Wrapped lines are not indented.
Example:
/**
* @fileoverview Description of file, its uses and information
* about its dependencies.
* @package
*/
7.6 Class comments
Classes, interfaces and records must be documented with a description and any
template parameters, implemented interfaces, visibility, or other appropriate
tags. The class description should provide the reader with enough information to
know how and when to use the class, as well as any additional considerations
necessary to correctly use the class. Textual descriptions may be omitted on the
constructor. @constructor
and @extends
annotations are not used with the
class
keyword unless the class is being used to declare an @interface
or
it extends a generic class.
/**
* A fancier event target that does cool things.
* @implements {Iterable<string>}
*/
class MyFancyTarget extends EventTarget {
/**
* @param {string} arg1 An argument that makes this more interesting.
* @param {!Array<number>} arg2 List of numbers to be processed.
*/
constructor(arg1, arg2) {
// ...
}
};
/**
* Records are also helpful.
* @extends {Iterator<TYPE>}
* @record
* @template TYPE
*/
class Listable {
/** @return {TYPE} The next item in line to be returned. */
next() {}
}
7.7 Enum and typedef comments
Enums and typedefs must be documented. Public enums and typedefs must have a non-empty description. Individual enum items may be documented with a JSDoc comment on the preceding line.
/**
* A useful type union, which is reused often.
* @typedef {!Bandersnatch|!BandersnatchType}
*/
let CoolUnionType;
/**
* Types of bandersnatches.
* @enum {string}
*/
const BandersnatchType = {
/** This kind is really frumious. */
FRUMIOUS: 'frumious',
/** The less-frumious kind. */
MANXOME: 'manxome',
};
Typedefs are useful for defining short record types, or aliases for unions,
complex functions, or generic types.
Typedefs should be avoided for record types with many fields, since they do not
allow documenting individual fields, nor using templates or recursive
references.
For large record types, prefer @record
.
7.8 Method and function comments
Parameter and return types must be documented. The this
type should be
documented when necessary. Method, parameter, and return descriptions (but not
types) may be omitted if they are obvious from the rest of the method’s JSDoc or
from its signature. Method descriptions should start with a sentence written in
the third person declarative voice. If a method overrides a superclass method,
it must include an @override
annotation. Overridden methods must include all
@param
and @return
annotations if any types are refined, but should omit
them if the types are all the same.
/** This is a class. */
class SomeClass extends SomeBaseClass {
/**
* Operates on an instance of MyClass and returns something.
* @param {!MyClass} obj An object that for some reason needs detailed
* explanation that spans multiple lines.
* @param {!OtherClass} obviousOtherClass
* @return {boolean} Whether something occurred.
*/
someMethod(obj, obviousOtherClass) { ... }
/** @override */
overriddenMethod(param) { ... }
}
/**
* Demonstrates how top-level functions follow the same rules. This one
* makes an array.
* @param {TYPE} arg
* @return {!Array<TYPE>}
* @template TYPE
*/
function makeArray(arg) { ... }
Anonymous functions do not require JSDoc, though parameter types may be specified inline if the automatic type inference is insufficient.
promise.then(
(/** !Array<number|string> */ items) => {
doSomethingWith(items);
return /** @type {string} */ (items[0]);
});
7.9 Property comments
Property types must be documented. The description may be omitted for private properties, if name and type provide enough documentation for understanding the code.
Publicly exported constants are commented the same way as properties. Explicit
types may be omitted for @const
properties initialized from an expression with
an obviously known type.
Tip: A @const
property’s type can be considered “obviously known” if it is
assigned directly from a constructor parameter with a declared type, or directly
from a function call with a declared return type. Non-const properties and
properties assigned from more complex expressions should have their types
declared explicitly.
/** My class. */
class MyClass {
/** @param {string=} someString */
constructor(someString = 'default string') {
/** @private @const */
this.someString_ = someString;
/** @private @const {!OtherType} */
this.someOtherThing_ = functionThatReturnsAThing();
/**
* Maximum number of things per pane.
* @type {number}
*/
this.someProperty = 4;
}
}
/**
* The number of times we'll try before giving up.
* @const
*/
MyClass.RETRY_COUNT = 33;
7.10 Type annotations
Type annotations are found on @param
, @return
, @this
, and @type
tags,
and optionally on @const
, @export
, and any visibility tags. Type
annotations attached to JSDoc tags must always be enclosed in braces.
7.10.1 Nullability
The type system defines modifiers !
and ?
for non-null and nullable,
respectively. Primitive types (undefined
, string
, number
, boolean
,
symbol
, and function(...): ...
) and record literals ({foo: string, bar:
number}
) are non-null by default. Do not add an explicit !
to these types.
Object types (Array
, Element
, MyClass
, etc) are nullable by default, but
cannot be immediately distinguished from a name that is @typedef
’d to a
non-null-by-default type. As such, all types except primitives and record
literals must be annotated explicitly with either ?
or !
to indicate whether
they are nullable or not.
7.10.2 Type Casts
In cases where type checking doesn't accurately infer the type of an expression, it is possible to tighten the type by adding a type annotation comment and enclosing the expression in parentheses. Note that the parentheses are required.
/** @type {number} */ (x)
7.10.3 Template Parameter Types
Always specify template parameters. This way compiler can do a better job and it makes it easier for readers to understand what code does.
Bad:
const /** !Object */ users = {};
const /** !Array */ books = [];
const /** !Promise */ response = ...;
Good:
const /** !Object<string, !User> */ users = {};
const /** !Array<string> */ books = [];
const /** !Promise<!Response> */ response = ...;
const /** !Promise<undefined> */ thisPromiseReturnsNothingButParameterIsStillUseful = ...;
const /** !Object<string, *> */ mapOfEverything = {};
Cases when template parameters should not be used:
Object
is used for type hierarchy and not as map-like structure.
7.11 Visibility annotations
Visibility annotations (@private
, @package
, @protected
) may be specified
in a @fileoverview
block, or on any exported symbol or property. Do not
specify visibility for local variables, whether within a function or at the top
level of a module. All @private
names must end with an underscore.
8 Policies
8.1 Issues unspecified by Google Style: Be Consistent!
For any style question that isn't settled definitively by this specification, prefer to do what the other code in the same file is already doing. If that doesn't resolve the question, consider emulating the other files in the same package.
8.2 Compiler warnings
8.2.1 Use a standard warning set
As far as possible projects should use --warning_level=VERBOSE
.
8.2.2 How to handle a warning
Before doing anything, make sure you understand exactly what the warning is telling you. If you're not positive why a warning is appearing, ask for help .
Once you understand the warning, attempt the following solutions in order:
- First, fix it or work around it. Make a strong attempt to actually address the warning, or find another way to accomplish the task that avoids the situation entirely.
- Otherwise, determine if it's a false alarm. If you are convinced that
the warning is invalid and that the code is actually safe and correct, add a
comment to convince the reader of this fact and apply the
@suppress
annotation. - Otherwise, leave a TODO comment. This is a last resort. If you do this, do not suppress the warning. The warning should be visible until it can be taken care of properly.
8.2.3 Suppress a warning at the narrowest reasonable scope
Warnings are suppressed at the narrowest reasonable scope, usually that of a single local variable or very small method. Often a variable or method is extracted for that reason alone.
Example
/** @suppress {uselessCode} Unrecognized 'use asm' declaration */
function fn() {
'use asm';
return 0;
}
Even a large number of suppressions in a class is still better than blinding the entire class to this type of warning.
8.3 Deprecation
Mark deprecated methods, classes or interfaces with @deprecated
annotations. A
deprecation comment must include simple, clear directions for people to fix
their call sites.
8.4 Code not in Google Style
You will occasionally encounter files in your codebase that are not in proper Google Style. These may have come from an acquisition, or may have been written before Google Style took a position on some issue, or may be in non-Google Style for any other reason.
8.4.1 Reformatting existing code
When updating the style of existing code, follow these guidelines.
- It is not required to change all existing code to meet current style guidelines. Reformatting existing code is a trade-off between code churn and consistency. Style rules evolve over time and these kinds of tweaks to maintain compliance would create unnecessary churn. However, if significant changes are being made to a file it is expected that the file will be in Google Style.
- Be careful not to allow opportunistic style fixes to muddle the focus of a CL. If you find yourself making a lot of style changes that aren’t critical to the central focus of a CL, promote those changes to a separate CL.
8.4.2 Newly added code: use Google Style
Brand new files use Google Style, regardless of the style choices of other files in the same package.
When adding new code to a file that is not in Google Style, reformatting the existing code first is recommended, subject to the advice in ??.
If this reformatting is not done, then new code should be as consistent as possible with existing code in the same file, but must not violate the style guide.
8.5 Local style rules
Teams and projects may adopt additional style rules beyond those in this document, but must accept that cleanup changes may not abide by these additional rules, and must not block such cleanup changes due to violating any additional rules. Beware of excessive rules which serve no purpose. The style guide does not seek to define style in every possible scenario and neither should you.
8.6 Generated code: mostly exempt
Source code generated by the build process is not required to be in Google Style. However, any generated identifiers that will be referenced from hand-written source code must follow the naming requirements. As a special exception, such identifiers are allowed to contain underscores, which may help to avoid conflicts with hand-written identifiers.
9 Appendices
9.1 JSDoc tag reference
JSDoc serves multiple purposes in JavaScript. In addition to being used to generate documentation it is also used to control tooling. The best known are the Closure Compiler type annotations.
9.1.1 Type annotations and other Closure Compiler annotations
Documentation for JSDoc used by the Closure Compiler is described in Annotating JavaScript for the Closure Compiler and Types in the Closure Type System.
9.1.2 Documentation annotations
In addition to the JSDoc described in Annotating JavaScript for the Closure Compiler the following tags are common and well supported by various documentation generations tools (such as JsDossier) for purely documentation purposes.
| Tag | Template & Examples | Description |
|---|---|---|
@author or @owner
| @author<EMAIL_ADDRESS>(First Last)
For example: /** * @fileoverview Utilities for handling textareas. * @author<EMAIL_ADDRESS>(Uthur Pendragon) */ | Document the author of a file or the owner of a test, generally only
used in the @fileoverview comment. The @owner tag is used by the
unit test dashboard to determine who owns the test results.
Not recommended. |
@bug
| @bug bugnumber
For example: /** @bug 1234567 */ function testSomething() { // … } | Indicates what bugs the given test function regression tests.
Multiple bugs should each have their own |
@code
| {@code ...}
For example: /** * Moves to the next position in the selection. * Throws {@code goog.iter.StopIteration} when it * passes the end of the range. * @return {!Node} The node at the next position. */ goog.dom.RangeIterator.prototype.next = function() { // … }; | Indicates that a term in a JSDoc description is code so it may be correctly formatted in generated documentation. |
@see
| @see Link
For example: /** * Adds a single item, recklessly. * @see #addSafely * @see goog.Collect * @see goog.RecklessAdder#add */ | Reference a lookup to another class function or method. |
@supported
| @supported Description
For example: /** * @fileoverview Event Manager * Provides an abstracted interface to the * browsers' event systems. * @supported IE10+, Chrome, Safari */ | Used in a fileoverview to indicate what browsers are supported by the file. |
@desc
| @desc Message description
For example: /** @desc Notifying a user that their account has been created. */ exports.MSG_ACCOUNT_CREATED = goog.getMsg( 'Your account has been successfully created.'); |
You may also see other types of JSDoc annotations in third-party code. These annotations appear in the JSDoc Toolkit Tag Reference but are not considered part of valid Google style.
9.1.3 Framework specific annotations
The following annotations are specific to a particular framework.
| Framework | Tag | Documentation |
|---|---|---|
| Angular 1 | @ngInject
| |
| Polymer | @polymerBehavior
| https://github.com/google/closure-compiler/wiki/Polymer-Pass |
9.1.4 Notes about standard Closure Compiler annotations
The following tags used to be standard but are now deprecated.
| Tag | Template & Examples | Description |
|---|---|---|
@expose
| @expose
| Deprecated. Do not use. Use @export and/or @nocollapse
instead.
|
@inheritDoc
| @inheritDoc
| Deprecated. Do not use. Use @override instead.
|
9.2 Commonly misunderstood style rules
Here is a collection of lesser-known or commonly misunderstood facts about
Google Style for JavaScript. (The following are true statements; this is not a
list of myths.
)
- Neither a copyright statement nor
@author
credit is required in a source file. (Neither is explicitly recommended, either.) - Aside from the constructor coming first
(??), there is no
hard and fast
rule governing how to order the members of a class (??). - Empty blocks can usually be represented concisely as
{}
, as detailed in (??). - The prime directive of line-wrapping is: prefer to break at a higher syntactic level (??).
- Non-ASCII characters are allowed in string literals, comments and Javadoc, and in fact are recommended when they make the code easier to read than the equivalent Unicode escape would (??).
9.3 Style-related tools
The following tools exist to support various aspects of Google Style.
9.3.1 Closure Compiler
This program performs type checking and other checks, optimizations and other transformations (such as ECMAScript 6 to ECMAScript 5 code lowering).
9.3.2 clang-format
This program reformats JavaScript source code into Google Style, and also follows a number of non-required but frequently readability-enhancing formatting practices.
clang-format
is not required. Authors are allowed to change its output, and
reviewers are allowed to ask for such changes; disputes are worked out in the
usual way. However, subtrees may choose to opt in to such enforcement locally.
9.3.3 Closure compiler linter
This program checks for a variety of missteps and anti-patterns.
9.3.4 Conformance framework
The JS Conformance Framework is a tool that is part of the Closure Compiler that provides developers a simple means to specify a set of additional checks to be run against their code base above the standard checks. Conformance checks can, for example, forbid access to a certain property, or calls to a certain function, or missing type information (unknowns).
These rules are commonly used to enforce critical restrictions (such as defining
globals, which could break the codebase) and security patterns (such as using
eval
or assigning to innerHTML
), or more loosely to improve code quality.
For additional information see the official documentation for the JS Conformance Framework.
9.4 Exceptions for legacy platforms
9.4.1 Overview
This section describes exceptions and additional rules to be followed when modern ECMAScript 6 syntax is not available to the code authors. Exceptions to the recommended style are required when ECMAScript 6 syntax is not possible and are outlined here:
- Use of
var
declarations is allowed - Use of
arguments
is allowed - Optional parameters without default values are allowed
9.4.2 Use var
<IP_ADDRESS> var
declarations are NOT block-scoped
var
declarations are scoped to the beginning of the nearest enclosing
function, script or module, which can cause unexpected behavior, especially with
function closures that reference var
declarations inside of loops. The
following code gives an example:
for (var i = 0; i < 3; ++i) {
var iteration = i;
setTimeout(function() { console.log(iteration); }, i*1000);
}
// logs 2, 2, 2 -- NOT 0, 1, 2
// because `iteration` is function-scoped, not local to the loop.
<IP_ADDRESS> Declare variables as close as possible to first use
Even though var
declarations are scoped to the beginning of the enclosing
function, var
declarations should be as close as possible to their first use,
for readability purposes. However, do not put a var
declaration inside a block
if that variable is referenced outside the block. For example:
function sillyFunction() {
var count = 0;
for (var x in y) {
// "count" could be declared here, but don't do that.
count++;
}
console.log(count + ' items in y');
}
<IP_ADDRESS> Use @const for constants variables
For global declarations where the const
keyword would be used, if it were
available, annotate the var
declaration with @const instead (this is optional
for local variables).
9.4.3 Do not use block scoped functions declarations
Do not do this:
if (x) {
function foo() {}
}
While most JavaScript VMs implemented before ECMAScript 6 support function declarations within blocks it was not standardized. Implementations were inconsistent with each other and with the now-standard ECMAScript 6 behavior for block scoped function declaration. ECMAScript 5 and prior only allow for function declarations in the root statement list of a script or function and explicitly ban them in block scopes in strict mode.
To get consistent behavior, instead use a var
initialized with a function
expression to define a function within a block:
if (x) {
var foo = function() {};
}
9.4.4 Dependency management with goog.provide
/goog.require
goog.provide
is deprecated. All new files should use goog.module
, even in
projects with existing goog.provide
usage. The following rules are for
pre-existing goog.provide files, only.
<IP_ADDRESS> Summary
- Place all
goog.provide
s first,goog.require
s second. Separate provides from requires with an empty line. - Sort the entries alphabetically (uppercase first).
- Don't wrap
goog.provide
andgoog.require
statements. Exceed 80 columns if necessary. - Only provide top-level symbols.
As of Oct 2016, goog.provide
/goog.require
dependency management is
deprecated. All new files, even in projects using goog.provide
for older
files, should use
goog.module
.
goog.provide
statements should be grouped together and placed first. All
goog.require
statements should follow. The two lists should be separated with
an empty line.
Similar to import statements in other languages, goog.provide
and
goog.require
statements should be written in a single line, even if they
exceed the 80 column line length limit.
The lines should be sorted alphabetically, with uppercase letters coming first:
goog.provide('namespace.MyClass');
goog.provide('namespace.helperFoo');
goog.require('an.extremelyLongNamespace.thatSomeoneThought.wouldBeNice.andNowItIsLonger.Than80Columns');
goog.require('goog.dom');
goog.require('goog.dom.TagName');
goog.require('goog.dom.classes');
goog.require('goog.dominoes');
All members defined on a class should be in the same file. Only top-level classes should be provided in a file that contains multiple members defined on the same class (e.g. enums, inner classes, etc).
Do this:
goog.provide('namespace.MyClass');
Not this:
goog.provide('namespace.MyClass');
goog.provide('namespace.MyClass.CONSTANT');
goog.provide('namespace.MyClass.Enum');
goog.provide('namespace.MyClass.InnerClass');
goog.provide('namespace.MyClass.TypeDef');
goog.provide('namespace.MyClass.staticMethod');
Members on namespaces may also be provided:
goog.provide('foo.bar');
goog.provide('foo.bar.CONSTANT');
goog.provide('foo.bar.method');
<IP_ADDRESS> Aliasing with goog.scope
goog.scope
is deprecated. New files should not use goog.scope
even in
projects with existing goog.scope usage.
goog.scope
may be used to shorten references to namespaced symbols in
code using goog.provide
/goog.require
dependency management.
Only one goog.scope
invocation may be added per file. Always place it in
the global scope.
The opening goog.scope(function() {
invocation must be preceded by exactly one
blank line and follow any goog.provide
statements, goog.require
statements,
or top-level comments. The invocation must be closed on the last line in the
file. Append // goog.scope
to the closing statement of the scope. Separate the
comment from the semicolon by two spaces.
Similar to C++ namespaces, do not indent under goog.scope
declarations.
Instead, continue from the 0 column.
Only make aliases for names that will not be re-assigned to another object (e.g., most constructors, enums, and namespaces). Do not do this (see below for how to alias a constructor):
goog.scope(function() {
var Button = goog.ui.Button;
Button = function() { ... };
...
Names must be the same as the last property of the global that they are aliasing.
goog.provide('my.module.SomeType');
goog.require('goog.dom');
goog.require('goog.ui.Button');
goog.scope(function() {
var Button = goog.ui.Button;
var dom = goog.dom;
// Alias new types after the constructor declaration.
my.module.SomeType = function() { ... };
var SomeType = my.module.SomeType;
// Declare methods on the prototype as usual:
SomeType.prototype.findButton = function() {
// Button as aliased above.
this.button = new Button(dom.getElement('my-button'));
};
...
}); // goog.scope


|
Scheduler
|
Typedefs | |
| typedef size_t | action_t |
| typedef size_t | state_t |
| typedef std::vector< statePosition_t > | StateInternal |
| typedef int | statePosition_t |
Copyright 2017 Jacques Florence All rights reserved. See License.txt file
| typedef size_t Mdp::action_t |
Definition at line 18 of file action_impl.h.
| typedef size_t Mdp::state_t |
| typedef std::vector<statePosition_t> Mdp::StateInternal |
Definition at line 24 of file stateSpace.h.
| typedef int Mdp::statePosition_t |
Definition at line 19 of file stateSpaceDimension.h.


Most build system modules and targets deal within the context of the current directory, however the Component module deals with components as a whole, so many of the targets produced by this module are stored in a location known to all subdirectories within a component build at the COMPONENT_ROOT level.
IMPORTRPM_TARGETS should be named for the imported RPM file,
IMPORTRPM_TARGETS will be built as a prerequisite to "depends" IMPORTRPM_TARGETS may be built in isolation by requesting the "component_import" target.
NOTE Despite appearing similar to DIST_TARGETS, this pattern target functions completely differently. The current DIST_TARGETS is deprecated, and will have its current form removed.
COMPONENT_ROOT=../.. BS_ROOT=$(COMPONENT_ROOT)/../build3 include $(BS_ROOT)/defines.mk IMPORTRPM_TARGETS=foo.rpm moof.rpm BULKDIST_TARGETS=nclib_dist moof.rpm_PKGFILE=/my_other_build/moof-new.rpm nclib_dist_MANIFEST=$(COMPONENT_ROOT)/nclib/$(BS_ARCH_TARGET_DIR)/nclib-epm.manifest include $(BS_ROOT)/rules.mk


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Preparation time
overnight
Cooking time
30 mins to 1 hour
Serves
Serves 2
Dietary
Oil infused with charred leeks is used to make a mayonnaise and served with fried mushrooms, grilled leeks and croûtons.
For the charred leek oil, heat a griddle. When hot, add the leeks cut-side down and cook until charred. Turn the leeks over and cook on the other side until soft. Place in a bowl with the oil and leave in a warm place (ideally around 50C/122F) for 4-5 hours. Then leave overnight to infuse. Strain the oil before using.
For the leek mayonnaise, in a food processor, blend the egg yolks and mustard to combine. With the motor running add the leek oil in a thin steady stream until the mixture emulsifies to form a mayonnaise. Add the white wine vinegar and pulse to combine. Season with salt, pepper and a little lemon juice, to taste. Store in the fridge until ready to serve.
For the leeks and girolles, season the whole leek with salt and pepper and place on a hot griddle until charred all over and soft. Transfer to a baking tray and cover with cling film to keep warm.
Season the baguette slices with salt and pepper and brush with olive oil. Toast both sides on the griddle to make croûtons.
Warm the remaining leek oil in a small pan set over a low heat. Gently lower the egg yolks into the oil and poach very gently for about six minutes.
Heat the butter in a frying pan and, when foaming, fry the girolles until soft. Add the vegetable stock, then turn off the heat and stir a little vinaigrette into the mixture.
To serve, cut the warm leek in half and remove the blackened outer layer. In shallow bowls, toss the leek in the remaining vinaigrette. Place the egg yolks on top, followed by the mushrooms and a spoonful of leek mayonnaise. If desired spoon over some of the cooking liquor from the mushrooms.
Garnish with the toasted baguette and herbs.


Home
Sales
Contacts
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Welcome to "Salmon Cookie Shop
Monday - Friday 6am-8pm
Contact information:
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Address: 2901 3rd Ave #300, Seattle, WA 98121
Phone:<PHONE_NUMBER>
cookiesSalmon@gmail.com


{{/* gotype: github.com/JustaPenguin/assetto-server-manager.raceWeekendListTemplateVars */}} {{ define "title" }}Race Weekends{{ end }} {{ define "content" }}
A Race Weekend is a group of sequential sessions that can be run at any time. For example, you could set up a Qualifying session to run on a Saturday, then the Race to follow it on a Sunday. Server Manager handles the starting grid for you, and lets you organise Entrants into splits based on their results and other factors!
{{ template "raceweekend-premium" dict "IsPremium" $.IsPremium }}| Name | Progress | Number of Sessions | Number of Entrants | Actions |
|---|---|---|---|---|
| {{ .Name }} | {{ int .Progress }}% | {{ len .Sessions }} | {{ len .GetEntryList }} | View Export {{ if WriteAccess }} Edit Delete {{ end }} |
| Name | Number of Sessions | Number of Entrants | Actions |
|---|---|---|---|
| {{ .Name }} | {{ len .Sessions }} | {{ len .GetEntryList }} | View Export {{ if WriteAccess }} Edit Delete {{ end }} |


Sorry, but your browser doesn't support this presentation software. Works best in Chrome or Safari.
Context Models
- Higher-order Markov or n-gram models.
- Implemented to arbitrary order, and over arbitrary events (using C++
templates).
- Implementation uses PPM for smoothing.
$$ \mathbb{P}(e' | e_1^k) =
\begin{cases}
\frac{C(e_1^k::e')}{1+C(e_1^k)} && e_1^k::e' \text{ seen} \\
\frac{1}{1+C(e_1^k)} \cdot \mathbb{P}(e' | e_2^k) && \text{otherwise}
\end{cases} $$


WITNESS LIST Civil Practices Committee February 24, 1997-1:30P State of the Judiciary On: McCormick, Michael (Tx. Court of Crim. App.) Phillips, Tom (Tx. Supreme Court)


To create an empty chart, you can use
which will use the API key stored locally on your system.
By default, Datawrapper will create an empty linechart, without a title. The function returns a dw_chart-object with the metadata-elements from the API. This object can be used to populate the chart_id
-argument in all other functions - which means you don’t have to deal with it. Just store the response from dw_create_chart()
in your R-environment.
To populate that chart with data, you can run
dw_data_to_chart(
x = DATAFRAME,
chart_id = CHART_ID_OR_dw_chart-object
)
which uploads an R data.frame to an Datawrapper chart.
The data.frame should already be in the right format, only including the expected columns for the chart. The API will asume, that the first row contains headers. If that’s not true, you have to edit the metadata afterwards:
dw_edit_chart(
chart_id = CHART_ID_OR_dw_chart-object,
title = "I'm a title",
data =
list(
`horizontal-header` = "false"
)
)
Datawrapper offers a lot of variability in editing it’s charts’ metadata. You can find a whole Documentation here.
To speed things up, the dw_edit_chart()
-function has some built-in arguments for common transformations:
title
intro
which is the text below the titleannotate
which is the text below the plotbyline
which is the name of the authorsource_name
which states the sourcesource_url
which links to the source - but only if a source_name
is providedIf you want to edit specific arguments in your plot, you can use the arguments data
, visualize
, describe
and publish
to include lists to the API call which change all possible settings in a chart, as shown in the example above.
When you’re finished editing your chart, you might want to publish it:
dw_publish_chart(
chart_id = CHART_ID_OR_dw_chart-object
)
This function returns a URL to the chart and the embed code, if you set the argument return_urls to TRUE
.
Or you might want to delete a chart:
dw_delete_chart(
chart_id = CHART_ID_OR_dw_chart-object
)
You can export charts as png - or even in pdf or svg, if you’re using a paid plan.
exported_chart <- dw_export_chart(
chart_id = CHART_ID_OR_dw_chart-object,
type = c("png", "pdf", "svg")
)


How to write for DWP Digital
{{releaseVersion | log }}DWP Digital’s vision is to 'change lives by providing security, extending opportunity and giving people in our society the support they need'.
As someone who writes for DWP Digital, your challenge is to:
- express the vision in a way that makes your colleagues feel excited to be part of it and makes people looking for career opportunities want to work here
- position the department as being modern and people-focused
You can do this in 2 ways.
1. Use language that's clear, consistent and human
You're writing for your colleagues or people who are interested in working for DWP. Make sure you use words that they'll understand easily. That means using the active voice, contractions and the first person. And avoiding jargon, abbreviations and acronyms.
For example, don't write:
"New technological devices are being rolled out to core sites in the near future."
Instead, try:
"If you work in one of these offices, you'll be given a new Surface Pro computer in July."
Everything you write for DWP Digital must follow:
2. Show don't tell
Let our work speak for itself. It doesn't need any spin. Share examples to show the reader what we're doing to achieve our vision. Don't tell them it's innovative or exciting - show them it is through the stories you tell.
There will be information you need to share that isn’t exciting. For example, you might need to tell people they must update their details for payroll. That’s OK. Be clear and tell them what they need to do.
For example, don't write:
"There's a cutting-edge new payroll system being introduced. Don't miss out - update your details today."
Instead, try:
"You must add your bank details to the new payroll system by Friday 30 September. If you need help, ask your line manager."
Before you publish your content, make sure:
- ☐ it's written with the user in mind
- ☐ it's in the active voice
- ☐ the title clearly tells the reader what the content is about
- ☐ the most important words are near the start of the title
- ☐ the first paragraph doesn't repeat the title
- ☐ the most important points for the reader are early in the content
- ☐ each paragraph is about one topic
- ☐ each paragraph is a maximum of 4 lines long
- ☐ subheadings, bullet points or numbers are used to break up chunks of information
- ☐ sentences are a maximum of 25 words long
- ☐ jargon, technical terms, acronyms and abbreviations are avoided (or, if absolutely necessary, explained)
- ☐ every word is essential
- ☐ you know how to measure its success
- ☐ it's been checked by someone else


{% extends 'events-base.html' %} {% block event_breadcrumb %}
Bootcamps are a more intensive 10 day introduction to programming or particular topics in technology. They're designed for you to jump quickly into programming and get a running start in new fields.
Our two-week bootcamps are designed as more advanced workforce training programs for women actively seeking a leg up in their field. Participants should come prepared to dive into the Linux Terminal, Python, Databases, Django, HTML, CSS, WordPress, and JavaScript with a focus on design and development of a complete web application. By the end of bootcamp, you will have a snazzy new program to show off your freshly honed programming skills.
We're currently setting up our Bootcamps project, we're looking for teachers and students. If you're interested in teaching or think you can get a group together for a particular topic, please get in touch!
GeekChic Programming encourages women to transform technology by applying the skills they learn in our programming workshops and classes to explore innovative solutions to real-world problems. Over the last three years, President Obama has continued to emphasize the importance of STEM in education reform. The White House is committed to expanding STEM education and career opportunities for underrepresented groups, including women and girls, and the global job marketplace shows that these technical skills are in extremely high demand. There is a demonstrated need for women in the fields of science, technology, engineering, and math, and software is at the center of every STEM project.
{% endblock %}