MDN will be in maintenance mode on Thursday September 21st, starting at 10 AM Pacific / 5 PM UTC, for about 1 hour.

The join() method joins all elements of an array (or an array-like object) into a string.

var a = ['Wind', 'Rain', 'Fire'];
a.join();    // 'Wind,Rain,Fire'
a.join('-'); // 'Wind-Rain-Fire'

Syntax

arr.join()
arr.join(separator)

Parameters

separator Optional
Specifies a string to separate each pair of adjacent elements of the array. The separator is converted to a string if necessary. If omitted, the array elements are separated with a comma (","). If separator is an empty string, all elements are joined without any characters in between them.

Return value

A string with all array elements joined. If arr.length is 0, the empty string is returned.

Description

The string conversions of all array elements are joined into one string. If an element is undefined or null, it is converted to the empty string.

Examples

Joining an array four different ways

The following example creates an array, a, with three elements, then joins the array four times: using the default separator, then a comma and a space, then a plus and an empty string.

var a = ['Wind', 'Rain', 'Fire'];
a.join();      // 'Wind,Rain,Fire'
a.join(', ');  // 'Wind, Rain, Fire'
a.join(' + '); // 'Wind + Rain + Fire'
a.join('');    // 'WindRainFire'

Specifications

Specification Status Comment
ECMAScript 1st Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.1.
ECMAScript 5.1 (ECMA-262)
The definition of 'Array.prototype.join' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Array.prototype.join' in that specification.
Standard  
ECMAScript Latest Draft (ECMA-262)
The definition of 'Array.prototype.join' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic Support1 (Yes)15.5 (Yes) (Yes)
FeatureAndroidChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic Support (Yes) (Yes) (Yes)1 (Yes) (Yes) (Yes)

See also