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The length property represents the length of a string.
Syntax
str.lengthDescription
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.
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 2017 Draft (ECMA-262) The definition of 'String.prototype.length' in that specification. |
Draft |
Browser compatibility
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|
| Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
| Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|
| Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |