A code example from the article https://www.joshwulf.com/blog/2020/03/why-array-map/

Array.prototype.map.js

// Production steps of ECMA-262, Edition 5, 15.4.4.19
// Reference: http://es5.github.io/#x15.4.4.19

if (!Array.prototype.map) {
  Array.prototype.map = function(callback/*, thisArg*/) {
    var T, A, k;
    if (this == null) {
      throw new TypeError('this is null or not defined');
    }
    var O = Object(this);
    var len = O.length >>> 0;
    if (typeof callback !== 'function') {
      throw new TypeError(callback + ' is not a function');
    }
    if (arguments.length > 1) {
      T = arguments[1];
    }
    A = new Array(len);
    k = 0;
    while (k < len) {
      var kValue, mappedValue;
      if (k in O) {
        kValue = O[k];
        mappedValue = callback.call(T, kValue, k, O);
        A[k] = mappedValue;
      }
      k++;
    }
    return A;
  };
}