javascript polyfills

polyfills.js

/**
 * Array map polyfill
 * @param {*} callback
 * @returns
 */
function myMap(callback) {
  let newArr = [];

  for (let i = 0; i < this.length; i++) {
    newArr.push(callback(this[i]));
  }
  return newArr;
}

Array.prototype.myMap = myMap;

let arr = [1, 2, 3, 4];
let newArray = arr.myMap((num) => {
  return num + 1;
});

/** Array reduce polyfill */
function myReduce(callback, initialValue) {
  if (typeof callback !== "function") {
    throw new TypeError("callback must be a function");
  }
  const array = this;

  const length = array.length;

  let accumulator = initialValue !== undefined ? initialValue : array[0];

  for (let i = 0; i < length; i++) {
    if (i in array) {
      accumulator = callback.call(undefined, accumulator, array[i], i, array);
    }
  }
}

/**
 * Arrray bind function
 * @param {*} context
 */
function myBind(context, ...args1) {
  let fn = this;
  return function (...args2) {
    return fn.apply(context, [...args1, ...args2]);
  };
}

Function.prototype.myBind = myBind;

function abc(num1, num2) {
  return num1 + num2;
}

let basic = {
  name: "test1",
  num: 123,
};

let newFunc = abc.mybind(basic, "jammu");
newFunc("hello");