The shift()
method removes the first element from an array and returns that removed element. This method changes the length of the array.
var a = [1, 2, 3]; var b = a.shift(); console.log(a); // [2, 3] console.log(b); // 1
Syntax
arr.shift()
Return value
The removed element from the array; undefined
if the array is empty.
Description
The shift
method removes the element at the zeroeth index and shifts the values at consecutive indexes down, then returns the removed value. If the length
property is 0, undefined
is returned.
shift
is intentionally generic; this method can be called or applied to objects resembling arrays. Objects which do not contain a length
property reflecting the last in a series of consecutive, zero-based numerical properties may not behave in any meaningful manner.
Examples
Removing an element from an array
The following code displays the myFish
array before and after removing its first element. It also displays the removed element:
var myFish = ['angel', 'clown', 'mandarin', 'surgeon']; console.log('myFish before:', JSON.stringify(myFish)); // myFish before: ['angel', 'clown', 'mandarin', 'surgeon'] var shifted = myFish.shift(); console.log('myFish after:', myFish); // myFish after: ['clown', 'mandarin', 'surgeon'] console.log('Removed this element:', shifted); // Removed this element: angel
Using shift() method in while loop
The shift() method is often used in condition inside while loop. In the following example every iteration will remove next element from an array, untill it will be empty:
var names = ["Andrew", "Edward", "Paul", "Chris" ,"John"]; while( (i = names.shift()) !== undefined ) { console.log(i); } // Andrew, Edward, Paul, Chris, John
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.shift' in that specification. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Array.prototype.shift' in that specification. |
Standard | |
ECMAScript Latest Draft (ECMA-262) The definition of 'Array.prototype.shift' in that specification. |
Living Standard |
Browser compatibility
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 1 | Yes | 1 | 5.5 | Yes | Yes |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | Yes | Yes | Yes | 4 | Yes | Yes | Yes |