//True array ['a','b','c'].concat(['4','5','6']); //["a", "b", "c", "4", "5", "6"] //arguments is not a true array function fakeArray(){ return ['a','b','c'].concat(arguments); } fakeArray('4','5','6'); //["a", "b", "c", { 0:'4', 1:'5', 2:'6'}]