Array.prototype.pop()

The pop() method removes the last element from an array and returns that element. This method changes the length of the array.

Syntax

pop()

Return value

The removed element from the array; undefined if the array is empty.

Description

The pop method removes the last element from an array and returns that value to the caller.

pop 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.

If you call pop() on an empty array, it returns undefined.

Array.prototype.shift() has similar behavior to pop, but applied to the first element in an array.

Examples

Removing the last element of an array

The following code creates the myFish array containing four elements, then removes its last element.

var myFish = ['angel', 'clown', 'mandarin', 'sturgeon'];

var popped = myFish.pop();

console.log(myFish); // ['angel', 'clown', 'mandarin' ]

console.log(popped); // 'sturgeon'

Using apply( ) or call ( ) on array-like objects

The following code creates the myFish array-like object containing four elements and a length parameter, then removes its last element and decrements the length parameter.

var myFish = {0:'angel', 1:'clown', 2:'mandarin', 3:'sturgeon', length: 4};

var popped = Array.prototype.pop.call(myFish); //same syntax for using apply( )

console.log(myFish); // {0:'angel', 1:'clown', 2:'mandarin', length: 3}

console.log(popped); // 'sturgeon'

Using an object in an array-like fashion

push and pop are intentionally generic, and we can use that to our advantage — as the following example shows.

Note that in this example, 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 and Array.prototype.pop to trick those methods into thinking we’re dealing with an array.

const collection = {
    length: 0,
    addElements: function(...elements) {
        // obj.length will be incremented automatically
        // every time an element is added.
        
        // Returning what push returns; that is
        // the new value of length property.
        return [].push.call(this, ...elements);
    },
    removeElement: function() {
        // obj.length will be decremented automatically
        // every time an element is removed.
        
        // Returning what pop returns; that is
        // the removed element.
        return [].pop.call(this);
    }
}

collection.addElements(10, 20, 30);
console.log(collection.length);  // 3
collection.removeElement();
console.log(collection.length);  // 2

Specifications

Browser compatibility

See also

• Array.prototype.push()
• Array.prototype.shift()
• Array.prototype.unshift()
• Array.prototype.concat()
• Array.prototype.splice()