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.

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

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.

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

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

const popped = myFish.pop();

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

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

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.

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

const 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'

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

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