From MDN site, https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter
function filterFn() {
            if (!Array.prototype.filter) {
                Array.prototype.filter = function (fun /*, thisArg*/) {
                    'use strict';

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

                    var t = Object(this);
                    var len = t.length >>> 0;
                    if (typeof fun !== 'function') {
                        throw new TypeError();
                    }

                    var res = [];
                    var thisArg = arguments.length >= 2 ? arguments[1] : void 0;
                    for (var i = 0; i < len; i++) {
                        if (i in t) {
                            var val = t[i];

                            // NOTE: Technically this should Object.defineProperty at
                            //       the next index, as push can be affected by
                            //       properties on Object.prototype and Array.prototype.
                            //       But that method's new, and collisions should be
                            //       rare, so use the more-compatible alternative.
                            if (fun.call(thisArg, val, i, t)) {
                                res.push(val);
                            }
                        }
                    }

                    return res;
                };
            }
        }