Enforce Quote Style (quotes)

JavaScript allows you to define strings in one of three ways: double quotes, single quotes, and backticks (as of ECMAScript 6). For example:

/*eslint-env es6*/

var double = "double";
var single = 'single';
var backtick = `backtick`;    // ES6 only

Each of these lines creates a string and, in some cases, can be used interchangeably. The choice of how to define strings in a codebase is a stylistic one outside of template literals (which allow embedded of expressions to be interpreted).

Many codebases require strings to be defined in a consistent manner.

Rule Details

This rule is aimed at ensuring consistency of string quotes and as such will report a problem when an inconsistent style is found.

Fixable: This rule is automatically fixable using the --fix flag on the command line.

The rule configuration takes up to two options:

  1. The first option is "double", "single" or "backtick" for double-quotes, single-quotes or backticks respectively. The default is "double".
  2. The second option is the "avoid-escape" flag. When using "avoid-escape", this rule will not report a problem when a string is using single-quotes or double-quotes so long as the string contains a quote that would have to be escaped otherwise. For example, if you specify "double" and "avoid-escape", the string 'He said, "hi!"' is not considered a problem because using double quotes for that string would require escaping the double quotes inside of the string. This option is off by default.

When using "single" or "double", template literals that don’t contain a substitution, don’t contain a line break and aren’t tagged templates, are flagged as problems, even with the "avoid-escape" option.

Configuration looks like this:

[2, "single", "avoid-escape"]

The following patterns are considered problems:

/*eslint quotes: [2, "double"]*/

var single = 'single';                                 /*error Strings must use doublequote.*/
var unescaped = 'a string containing "double" quotes'; /*error Strings must use doublequote.*/

/*eslint quotes: [2, "single"]*/

var double = "double";                                 /*error Strings must use singlequote.*/
var unescaped = "a string containing 'single' quotes"; /*error Strings must use singlequote.*/

/*eslint quotes: [2, "double", "avoid-escape"]*/

var single = 'single'; /*error Strings must use doublequote.*/
var single = `single`; /*error Strings must use doublequote.*/

/*eslint quotes: [2, "single", "avoid-escape"]*/

var double = "double"; /*error Strings must use singlequote.*/
var double = `double`; /*error Strings must use singlequote.*/

/*eslint quotes: [2, "backtick"]*/

var single = 'single';                             /*error Strings must use backtick.*/
var double = "double";                             /*error Strings must use backtick.*/
var unescaped = 'a string containing `backticks`'; /*error Strings must use backtick.*/

/*eslint quotes: [2, "backtick", "avoid-escape"]*/

var single = 'single'; /*error Strings must use backtick.*/
var double = "double"; /*error Strings must use backtick.*/

The following patterns are not considered problems:

/*eslint quotes: [2, "double"]*/
/*eslint-env es6*/

var double = "double";
var backtick = `back\ntick`;  // backticks are allowed due to newline
var backtick = tag`backtick`; // backticks are allowed due to tag

/*eslint quotes: [2, "single"]*/
/*eslint-env es6*/

var single = 'single';
var backtick = `back${x}tick`; // backticks are allowed due to substitution

/*eslint quotes: [2, "double", "avoid-escape"]*/

var single = 'a string containing "double" quotes';

/*eslint quotes: [2, "single", "avoid-escape"]*/

var double = "a string containing 'single' quotes";

/*eslint quotes: [2, "backtick"]*/
/*eslint-env es6*/

var backtick = `backtick`;

/*eslint quotes: [2, "backtick", "avoid-escape"]*/

var double = "a string containing `backtick` quotes"

When Not To Use It

If you do not need consistency in your string styles, you can safely disable this rule.

Version

This rule was introduced in ESLint 0.0.7.

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