string.length

The length property represents the length of a string.

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.

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

See also

• JavaScript String.length and Internationalizing Web Applications