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;
                };
            }
        }
function filterFn() {
            if (!Array.prototype.filter) {
                Array.prototype.filter = function (fun ) {
                    '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];

                            
                            
                            
                            
                            
                            if (fun.call(thisArg, val, i, t)) {
                                res.push(val);
                            }
                        }
                    }

                    return res;
                };
            }
        }
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 ; } ; } }
From MDN site, https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter
From MDN site https : // developer . mozilla . org / en - US / docs / Web / JavaScript / Reference / Global_Objects / Array / filter