One possible implementation could be:

function customPush() {
  // DO NOT REMOVE
  'use strict';

  // Write your solution below
  if (this === null || this === undefined) {
    throw new TypeError(
      'Array.prototype.customUnshift called on null or undefined'
    );
  }

  var list = Object(this);
  var length = list.length || 0;
  var argumentsLength = arguments.length;

  if (!argumentsLength) {
    return length;
  }

  for (let i = 0; i &lt; argumentsLength; i++) {
    this[i + length] = arguments[i];
  }

  console.log(this);

  this.length = length + argumentsLength;

  return this.length;
}

Array.prototype.customPush = customPush;

How to implement Array.prototype.push? JavaScript Interview Question | Problem Solving | JavaScript Polyfills

@Yomesh Gupta