Javascript - Array pop polyfill code

Question

If I wanted to write the pop function from scratch what would be the most efficient way? The main issue also is how do I return the originating array without the popped element?

Array.prototype.pop = function () {
 var myArray = this;
 var length = myArray.length;
 var element = myArray[length-1];
 myArray = myArray.slice(0,length-1);
 return element;
}
var hello = [1,2,3,4,5];
hello.pop();
5
console.log(hello)
[1, 2, 3, 4, 5]

• hereandnow78: so you want a polyfill for pop? returning the last element, and changing your array?
• Andrew Templeton: "most efficient way" : see the jsperf answer, the one I put is fastest possible polyfill (still 10x slower :P ). I assume this is just for learning

Answer 1

Use splice instead of slice - slice doesn't modify the original array, whereas splice does.

That said, since you're removing the last element, it would be return myArray.splice(length-1,1);... which is essentially an alias for return myArray.pop() in the first place.

Alternatively, try:

var element = myArray[length-1];
myArray.length = length-1;
return element;

• Andrew Templeton: The myArray.length = length-1 does not work for empty arrays and throws uncaught RangeError: Invalid array length exceptions, and the splice call in your code needs to access [0] or else it returns a single element or zero element array, instead of the value itself or undefined. :(

Answer 2

Short and sweet:

Array.prototype.foo = function(){
 return this.splice(this.length-1)[0];
};

Returns last element or undefined if zero length and modifies the array itself.

Answer 3

Ahh performance... Why do you need that polyfill? Array.prototype.pop is widely supportet!

Anyways I created a little perf test to check that: http://jsperf.com/manual-pop

• Andrew Templeton: I like the jsperf enthusiasm though :)

Answer 4

Array.prototype.pop=Array.prototype.pop||function(){
 const len = this.length;
 const itemToBePopped=this[len-1];
 this.splice(len-1,1);
 return itemToBePopped;
}