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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 elements 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.
The only native, array-like objects are strings, although they are not suitable in applications of this method, as strings are immutable.
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.
var sports = ['soccer', 'baseball']; var 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.
var vegetables = ['parsnip', 'potato']; var 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.
var 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 | Status | Comment |
---|---|---|
ECMAScript 3rd Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.2. |
ECMAScript 5.1 (ECMA-262) The definition of 'Array.prototype.push' in that specification. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Array.prototype.push' in that specification. |
Standard | |
ECMAScript 2017 Draft (ECMA-262) The definition of 'Array.prototype.push' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 1.0 | 1.0 (1.7 or earlier) | 5.5 | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |