Just as we have snippet compiler to test a C# code quickly, I can also do the same for javascript in chrome debugger tools and Firebug (firefox).
I would be more interested in a tool or some online tool which can run a small piece of javascript and tell if it properly runs in prominent browsers and the result.
UPDATE:
I'm a developer and not tester. I don't want to install all browsers on my PC. I like chrome and I can debug/test (for syntax/result) almost every javascript quickly in chrome by just clicking Ctrl+Shift+J
and pasting my javascript in its console. But that will just test if it works in chrome. I'm not interested in creating a library right now. Google and Stackoverflow helps me get the greatest and latest javascript for a specific task very quickly.