The length
property of a String
object indicates the length of a string, in UTF-16 code units.
Syntax
str.length
Description
This property returns the number of code units in the string. UTF-16, the string format used by JavaScript, uses a single 16-bit code unit to represent the most common characters, but needs to use two code units for less commonly-used characters, so it's possible for the value returned by length
to not match the actual number of characters in the string.
ECMASCript 2016 (ed. 7) established a maximum length of 2^53 - 1
elements. Previously, no maximum length was specified.
For an empty string, length
is 0.
The static property String.length
returns the value 1.
Examples
Basic usage
var x = 'Mozilla'; var empty = ''; console.log('Mozilla is ' + x.length + ' code units long'); /* "Mozilla is 7 code units long" */ console.log('The empty string has a length of ' + empty.length); /* "The empty string has a length of 0" */
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 1st Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.0. |
ECMAScript 5.1 (ECMA-262) The definition of 'String.prototype.length' in that specification. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'String.prototype.length' in that specification. |
Standard | |
ECMAScript Latest Draft (ECMA-262) The definition of 'String.prototype.length' in that specification. |
Living Standard |
Browser compatibility
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | Yes | Yes | Yes | Yes | Yes | Yes |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | Yes | Yes | Yes | Yes | Yes | Yes | Yes |