Detect unused variables with JsHint

JsHint (and so does JSLint) has an option called unused to detect unused variables and parameters.

For instance if you have the SublimeLInter package installed, you will see a message like this:

It also helps me a lot to detected unused parameters, an example of this is when I write asynchronous unit tests:

sometimes I just forget calling the done() but the linter gives me this quick feedback.