The localeCompare()
method returns a number indicating whether a reference string comes before, or after, or is the same as the given string in sort order.
String.prototype.localeCompare()
Try it
The new locales
and options
arguments let applications specify the language whose sort order should be used and customize the behavior of the function. In older implementations, which ignore the locales
and options
arguments, the locale and sort order used are entirely implementation-dependent.
Syntax
localeCompare(compareString) localeCompare(compareString, locales) localeCompare(compareString, locales, options)
Parameters
-
compareString
-
The string against which the
referenceStr
is compared. -
locales
andoptions
-
These arguments customize the behavior of the function and let applications specify the language whose formatting conventions should be used. In implementations which ignore the
locales
andoptions
arguments, the locale used and the form of the string returned are entirely implementation-dependent.See the
Intl.Collator()
constructor for details on these parameters and how to use them.
Return value
A negative number if referenceStr
occurs before compareString
; positive if the referenceStr
occurs after compareString
; 0
if they are equivalent.
Description
Returns an integer indicating whether the referenceStr
comes before, after or is equivalent to the compareString
.
- Negative when the
referenceStr
occurs beforecompareString
- Positive when the
referenceStr
occurs aftercompareString
- Returns
0
if they are equivalent
Warning: Do not rely on exact return values of -1
or 1
!
Negative and positive integer results vary between browsers (as well as between browser versions) because the W3C specification only mandates negative and positive values. Some browsers may return -2
or 2
, or even some other negative or positive value.
Performance
When comparing large numbers of strings, such as in sorting large arrays, it is better to create an Intl.Collator
object and use the function provided by its compare
property.
Examples
Using localeCompare()
// The letter "a" is before "c" yielding a negative value 'a'.localeCompare('c'); // -2 or -1 (or some other negative value) // Alphabetically the word "check" comes after "against" yielding a positive value 'check'.localeCompare('against'); // 2 or 1 (or some other positive value) // "a" and "a" are equivalent yielding a neutral value of zero 'a'.localeCompare('a'); // 0
Sort an array
localeCompare()
enables case-insensitive sorting for an array.
let items = ['réservé', 'Premier', 'Cliché', 'communiqué', 'café', 'Adieu']; items.sort( (a, b) => a.localeCompare(b, 'fr', { ignorePunctuation: true })); // ['Adieu', 'café', 'Cliché', 'communiqué', 'Premier', 'réservé']
Check browser support for extended arguments
The locales
and options
arguments are not supported in all browsers yet.
To check whether an implementation supports them, use the "i"
argument (a requirement that illegal language tags are rejected) and look for a RangeError
exception:
function localeCompareSupportsLocales() { try { 'foo'.localeCompare('bar', 'i'); } catch (e) { return e.name === 'RangeError'; } return false; }
Using locales
The results provided by localeCompare()
vary between languages. In order to get the sort order of the language used in the user interface of your application, make sure to specify that language (and possibly some fallback languages) using the locales
argument:
console.log('ä'.localeCompare('z', 'de')); // a negative value: in German, ä sorts before z console.log('ä'.localeCompare('z', 'sv')); // a positive value: in Swedish, ä sorts after z
Using options
The results provided by localeCompare()
can be customized using the options
argument:
// in German, ä has a as the base letter console.log('ä'.localeCompare('a', 'de', { sensitivity: 'base' })); // 0 // in Swedish, ä and a are separate base letters console.log('ä'.localeCompare('a', 'sv', { sensitivity: 'base' })); // a positive value
Numeric sorting
// by default, "2" > "10" console.log("2".localeCompare("10")); // 1 // numeric using options: console.log("2".localeCompare("10", undefined, { numeric: true })); // -1 // numeric using locales tag: console.log("2".localeCompare("10", "en-u-kn-true")); // -1
Specifications
Specification |
---|
ECMAScript Language Specification # sec-string.prototype.localecompare |
ECMAScript Internationalization API Specification # sup-String.prototype.localeCompare |
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
localeCompare |
1
|
12
|
1
|
5.5
|
7
|
3
|
1
|
18
|
4
|
10.1
|
1
|
1.0
|
1.0
|
0.10.0
|
locales |
24
|
12
|
29
|
11
|
15
|
10
|
No
|
26
|
56
|
No
|
10
|
1.5
|
1.8
1.0-1.8
Only the locale data for
en-US is available.
|
13.0.0
0.12.0
Before version 13.0.0, only the locale data for
en-US is available by default. When other locales are specified, the function silently falls back to
en-US . To make full ICU (locale) data available before version 13, see
Node.js documentation on the --with-intl option and how to provide the data.
|
options |
24
|
12
|
29
|
11
|
15
|
10
|
No
|
26
|
56
|
No
|
10
|
1.5
|
1.0
|
0.12.0
|
See also
© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare