CoffeeScript checking if key exist in object

key-obj.litcoffee

You would think it works just like JavaScript:

'pushState' in window.history

But this actually compiles to:

var __indexOf = [].indexOf || function(item) { for (var i = 0, l = this.length; i < l; i++) { if (i in this && this[i] === item) return i; } return -1; };
__indexOf.call(window.history, 'pushState') >= 0;

What you want to do is use of instead of in:

'pushState' of window.history

which compiles as intended:

'pushState' in window.history;