Your code isn’t working because you are not initializing bar:
var bar = [];
You also forgot to declare your i variable, which can be problematic, for example if the code is inside a function, i will end up being a global variable (always use var :).
But, you can avoid the loop, simply by using the slice method to create a copy of your first array:
var arr = ["apple","banana","canaple"];
var bar = arr.slice();