JavaScript 1.7 is a language update introducing several new features, in particular generators, iterators, array comprehensions, let expressions, and destructuring assignment.
使用 JavaScript 1.7
为了使用 JavaScript 1.7的一些新特性，你需要明确指出你希望使用 JavaScript 1.7。在HTML 或XUL code中，使用：
When using the JavaScript shell, you need to set the version you wish to use using the -version 170 switch on the command line or using the version() function:
version(170);
The features that require the use of the new keywords "yield" and "let" require you to specify version 1.7 because existing code might use those keywords as variable or function names. The features that do not introduce new keywords (destructuring assignment and array comprehensions) can be used without specifying the JavaScript version.
JavaScript 1.7的新特性
The following features added with JavaScript 1.7 were not part of an ECMA-262 standard at the time. In more recent Firefox versions, the implementation is updated to work with semantics as specified in ECMAScript Edition 6. Please see the reference pages for differences.
- Iterators and generators
- Array comprehensions
letstatement- Destructuring assignment
Support for JS1.7 style destructuring for-in is dropped in Gecko 40 (bug 1083498).