Javascript 1.7

JavaScript 1.7 is a language update introducing several new features, in particular generators, iterators, array comprehensions, let expressions, and destructuring assignment.

MDN Javascript 1.7

In order to use some of the new features of JavaScript 1.7, you need to specify that you wish to use JavaScript 1.7

<script type="application/javascript;version=1.7">
//Your javascript 1.7 here