Version is a major update that includes significant improvements and many On the server, you don’t need a compiler-you can start using for– of in io.js (and Node, with the -harmony option) today.The developers behind Node.js released version 4.0 last week. If you’d like to use this new syntax on the web, but you need to support IE and Safari, you can use a compiler like Babel or Google’s Traceur to translate your ES6 code to Web-friendly ES5. It also works in Microsoft’s Spartan browser, but not in shipping versions of IE. It’s supported in Chrome if you go to chrome://flags and enable “Experimental JavaScript”. The for– of loop is supported in all current Firefox releases. for– of is easy to use, but there is a lot going on behind the scenes.
We could add that, but I think it would obscure what’s going on rather than illuminate it. Here is a rough equivalent, using the underlying methods and a few temporary variables: Now that we have all the details, we can take a simple for– of loop and rewrite it in terms of the underlying method calls. Most iterator objects won’t need to implement it.throw(exc) is even more of a special case: for– of never calls it at all. return() if it needs to do some cleanup or free up resources it was using. return() if the loop exits prematurely, due to an exception or a break or return statement. But all three designs are fundamentally returning the same information.Īn iterator object can also implement optional. next() method that throws StopIteration when there are no more values. value properties, is superficially different from how iterators work in other languages. Of course, a typical iterator will not be quite this trivial. How do you loop over the elements of an array? When JavaScript was introduced, twenty years ago, you would do it like this:įor (var index = 0 index < myArray.length index++) will be an infinite loop.
ES6 In Depth is a series on new features being added to the JavaScript programming language in the 6th Edition of the ECMAScript standard, ES6 for short.
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