Array.prototype.lastIndexOf()

const animals = ["Dodo", "Tiger", "Penguin", "Dodo"];

console.log(animals.lastIndexOf("Dodo"));
// Expected output: 3

console.log(animals.lastIndexOf("Tiger"));
// Expected output: 1

var array = [2, 5, 9, 2];
array.lastIndexOf(2); // 3
array.lastIndexOf(7); // -1
array.lastIndexOf(2, 3); // 3
array.lastIndexOf(2, 2); // 0
array.lastIndexOf(2, -2); // 0
array.lastIndexOf(2, -1); // 3

var indices = [];
var array = ["a", "b", "a", "c", "a", "d"];
var element = "a";
var idx = array.lastIndexOf(element);
while (idx != -1) {
  indices.push(idx);
  idx = idx > 0 ? array.lastIndexOf(element, idx - 1) : -1;
}

console.log(indices);
// [4, 2, 0]

//   ECMA-262, 5- , 15.4.4.15
//  (en): http://es5.github.io/#x15.4.4.15
//  (ru): http://es5.javascript.ru/x15.4.html#x15.4.4.15
if (!Array.prototype.lastIndexOf) {
  Array.prototype.lastIndexOf = function (searchElement /*, fromIndex*/) {
    "use strict";

    if (this === void 0 || this === null) {
      throw new TypeError();
    }

    var n,
      k,
      t = Object(this),
      len = t.length >>> 0;
    if (len === 0) {
      return -1;
    }

    n = len - 1;
    if (arguments.length > 1) {
      n = Number(arguments[1]);
      if (n != n) {
        n = 0;
      } else if (n != 0 && n != 1 / 0 && n != -(1 / 0)) {
        n = (n > 0 || -1) * Math.floor(Math.abs(n));
      }
    }

    for (k = n >= 0 ? Math.min(n, len - 1) : len - Math.abs(n); k >= 0; k--) {
      if (k in t && t[k] === searchElement) {
        return k;
      }
    }
    return -1;
  };
}