Yes: for each (...) -> It's not supported anywhere, so forget it. for (var x in a) -> x is the key, so it's kind of inconvenient. You have to watch out for in

Yes: for each (...) -> It's not supported anywhere, so forget it. for (var x in a) -> x is the key, so it's kind of inconvenient. You have to watch out for inherited properties/methods so one should check for a.hasOwnProperty(x). for (var x of a) -> It has mostly no gotchas. Only poor browser support. .forEach only works with arrays and from ES5 on. You have the good old "this"/scope gotcha.