Array.isArray = function(arg) {
   return Object.prototype.toString.call(arg) === '[object Array]';
};

Array.from = (function () {
       var symbolIterator;
       try {
           symbolIterator = Symbol.iterator
               ? Symbol.iterator
               : 'Symbol(Symbol.iterator)';
       } catch {
           symbolIterator = 'Symbol(Symbol.iterator)';
       }

       var toStr = Object.prototype.toString;
       var isCallable = function (fn) {
           return (
               typeof fn === 'function' ||
               toStr.call(fn) === '[object Function]'
           );
       };
       var toInteger = function (value) {
           var number = Number(value);
           if (isNaN(number)) return 0;
           if (number === 0 || !isFinite(number)) return number;
           return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number));
       };
       var maxSafeInteger = Math.pow(2, 53) - 1;
       var toLength = function (value) {
           var len = toInteger(value);
           return Math.min(Math.max(len, 0), maxSafeInteger);
       };

       var setGetItemHandler = function setGetItemHandler(isIterator, items) {
           var iterator = isIterator && items[symbolIterator]();
           return function getItem(k) {
               return isIterator ? iterator.next() : items[k];
           };
       };

       var getArray = function getArray(
           T,
           A,
           len,
           getItem,
           isIterator,
           mapFn
       ) {
           // 16. Let k be 0.
           var k = 0;

           // 17. Repeat, while k < len… or while iterator is done (also steps a - h)
           while (k < len || isIterator) {
               var item = getItem(k);
               var kValue = isIterator ? item.value : item;

               if (isIterator && item.done) {
                   return A;
               } else {
                   if (mapFn) {
                       A[k] =
                           typeof T === 'undefined'
                               ? mapFn(kValue, k)
                               : mapFn.call(T, kValue, k);
                   } else {
                       A[k] = kValue;
                   }
               }
               k += 1;
           }

           if (isIterator) {
               throw new TypeError(
                   'Array.from: provided arrayLike or iterator has length more then 2 ** 52 - 1'
               );
           } else {
               A.length = len;
           }

           return A;
       };

       // The length property of the from method is 1.
       return function from(arrayLikeOrIterator /*, mapFn, thisArg */) {
           // 1. Let C be the this value.
           var C = this;

           // 2. Let items be ToObject(arrayLikeOrIterator).
           var items = Object(arrayLikeOrIterator);
           var isIterator = isCallable(items[symbolIterator]);

           // 3. ReturnIfAbrupt(items).
           if (arrayLikeOrIterator == null && !isIterator) {
               throw new TypeError(
                   'Array.from requires an array-like object or iterator - not null or undefined'
               );
           }

           // 4. If mapfn is undefined, then let mapping be false.
           var mapFn = arguments.length > 1 ? arguments[1] : void undefined;
           var T;
           if (typeof mapFn !== 'undefined') {
               // 5. else
               // 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
               if (!isCallable(mapFn)) {
                   throw new TypeError(
                       'Array.from: when provided, the second argument must be a function'
                   );
               }

               // 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
               if (arguments.length > 2) {
                   T = arguments[2];
               }
           }

           // 10. Let lenValue be Get(items, "length").
           // 11. Let len be ToLength(lenValue).
           var len = toLength(items.length);

           // 13. If IsConstructor(C) is true, then
           // 13. a. Let A be the result of calling the [[Construct]] internal method
           // of C with an argument list containing the single item len.
           // 14. a. Else, Let A be ArrayCreate(len).
           var A = isCallable(C) ? Object(new C(len)) : new Array(len);

           return getArray(
               T,
               A,
               len,
               setGetItemHandler(isIterator, items),
               isIterator,
               mapFn
           );
       };
   })();

Array.of = function() {
  return Array.prototype.slice.call(arguments);
  // Or 
  let vals = [];
  for(let prop in arguments){
      vals.push(arguments[prop]);
  }
  return vals;
}