Whenever I open up the JavaScript Shell 1.4 to test some JavaScript out, I don’t like that I have to use the default JavaScript version while testing out code. Generators, let expressions, and various other improvements to JavaScript can be pretty useful but they require an explicit JavaScript version to be declared, so I modified it and added support that will allow JavaScript code up to 2.0 (you can test higher versions by increasing _JS_version_check.end). I call it JavaScript Shell 1.4 Extended. Think of it as the unofficial 1.5 version. If you want the bookmarklet, it’s on this bookmarklet page.

This works by redefining the main shell input eval function multiple times under different JavaScript versions, incrementing by 0.1 for each tag added (they are later removed).

There are also a few other various modifications which you can read about on my JavaScript Shell Extended project page.