Array.prototype.shift()
The shift()
method removes the first
element from an array and returns that removed element. This method changes the length
of the array.
Syntax
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.
Array.prototype.pop()
has similar behavior to shift
, but
applied to the last element in an array.
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:
const myFish = ['angel', 'clown', 'mandarin', 'surgeon'];
console.log('myFish before:', JSON.stringify(myFish));
// myFish before: ['angel', 'clown', 'mandarin', 'surgeon']
const 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 the next element from an array, until it is empty:
const names = ["Andrew", "Edward", "Paul", "Chris" ,"John"];
while( typeof (i = names.shift()) !== 'undefined' ) {
console.log(i);
}
// Andrew, Edward, Paul, Chris, John
Specifications
Specification |
---|
ECMAScript Language Specification # sec-array.prototype.shift |
Browser compatibility
BCD tables only load in the browser