Check out WebStorm 8 integration: lots of new features and fixed bugs, significant performance and usability improvements
You can also try standalone web UI version () (please note that the WebStorm version is far more stable and production ready, while the web UI version is more like a preview and not actively maintained at the moment)
Want to know what exactly happens when you click some button or run some unit test on any platform/device/browser? Whether it's your codebase or any other website scripts, spy-js allows you to trace the code you've just executed. You start from an event that triggered code execution, progress to the event javascript stack trace, end up in highlighted source code statements.
Ever spent several minutes trying to reproduce some bug and then realised that you didn't set required breakpoint? Tired of stepping into minified jQuery? spy-js allows you to select only scripts and events you're interested in, run your scenario and then inspect collected runtime data like function parameters, return values and exceptions to make your debugging easier.
Wondering what is slowing down your front-end or what to optimize in your code to get better javascript performance? Want to continuously see how changes being introduced are affecting code execution speed? With spy-js you can quickly get an idea of how long do certain events and functions take to execute and find good candidates for your javascript tuning.