Array.prototype.push()

The push() method adds one or more elements to the end of an array and returns the new length of the array.

Syntax

arr.push(element1[, ...[, elementN]])

Parameters

elementN
The element(s) to add to the end of the array.

Return value

The new length property of the object upon which the method was called.

Description

The push method appends values to an array.

push is intentionally generic. This method can be used with call() or apply() on objects resembling arrays. The push method relies on a length property to determine where to start inserting the given values. If the length property cannot be converted into a number, the index used is 0. This includes the possibility of length being nonexistent, in which case length will also be created.

Although strings are native, Array-like objects, they are not suitable in applications of this method, as strings are immutable.  Similarly for the native, Array-like object arguments.

Examples

Adding elements to an array

The following code creates the sports array containing two elements, then appends two elements to it. The total variable contains the new length of the array.

let sports = ['soccer', 'baseball']
let total = sports.push('football', 'swimming')

console.log(sports)  // ['soccer', 'baseball', 'football', 'swimming']
console.log(total)   // 4

Merging two arrays

This example uses apply() to push all elements from a second array.

Do not use this method if the second array (moreVegs in the example) is very large, because the maximum number of parameters that one function can take is limited in practice. See apply() for more details.

let vegetables = ['parsnip', 'potato']
let moreVegs = ['celery', 'beetroot']

// Merge the second array into the first one
// Equivalent to vegetables.push('celery', 'beetroot')
Array.prototype.push.apply(vegetables, moreVegs)

console.log(vegetables)  // ['parsnip', 'potato', 'celery', 'beetroot']

Using an object in an array-like fashion

As mentioned above, push is intentionally generic, and we can use that to our advantage. Array.prototype.push can work on an object just fine, as this example shows.

Note that we don't create an array to store a collection of objects. Instead, we store the collection on the object itself and use call on Array.prototype.push to trick the method into thinking we are dealing with an array—and it just works, thanks to the way JavaScript allows us to establish the execution context however we please.

let obj = {
    length: 0,

    addElem: function addElem(elem) {
        // obj.length is automatically incremented 
        // every time an element is added.
        [].push.call(this, elem)
    }
}

// Let's add some empty objects just to illustrate.
obj.addElem({})
obj.addElem({})
console.log(obj.length)
// → 2

Note that although obj is not an array, the method push successfully incremented obj's length property just like if we were dealing with an actual array.

Specifications

Specification
ECMAScript Latest Draft (ECMA-262)
The definition of 'Array.prototype.push' in that specification.

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
pushChrome Full support 1Edge Full support 12Firefox Full support 1IE Full support 5.5Opera Full support 4Safari Full support 1WebView Android Full support 1Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support 10.1Safari iOS Full support 1Samsung Internet Android Full support 1.0nodejs Full support Yes

Legend

Full support  
Full support

See also