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

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'

Joining an array-like object

The following example joins array-like object (arguments), by calling Function.prototype.call on Array.prototype.join.

function f(a, b, c) {
  var s = Array.prototype.join.call(arguments);
  console.log(s); // '1,a,true'
}
f(1, 'a', true);

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 Yes15.5 Yes Yes
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support Yes Yes Yes4 Yes Yes Yes

See also