Looks good.

Except JSHint doesn't like this (function in a loop)...

    for (i = 0; i < cbs.length; i++) {
      cb = cbs[i];
      // Force async
      setTimeout(function() {
        cb(res);
      },0);
    }

Not sure what we can do about that though – could swap it round so the loop's in a single call to the timeout function, but then all the callbacks would be synchronous with each other, which probably isn't ideal.

I agree the documentation should focus on async tests, but I don't think we should categorically say it's not supported for sync tests... maybe just don't mention sync at all, or say something like:

If you call Modernizr.on() for synchronous tests the callback will be invoked on the next tick, however we recommend handling synchronous tests synchronously where possible for speed and consistency.

An extra thought: how about renaming src/addTest to src/resolveAsyncTest or similar, to avoid confusion with the (synchronous) Modernizr.addTest?

JSHint doesn't like this (function in a loop)

I say we just add the exception comment :D

I don't think we should categorically say it's not supported

Right. Just undocumented. The note is good too.

An extra thought: how about renaming src/addTest to src/resolveAsyncTest

We have a lot of docs on adding your own test with addTest - perhaps we should expose it as an alias? I agree that it's confusing, but in the past it's the only mechanism people had for adding tests.

Testing wise I think we should include sinon.js so we can mock setTimeout and spy on the on method. Makes async testing less stabby.

We have a lot of docs on adding your own test with addTest - perhaps we should expose it as an alias? I agree that it's confusing, but in the past it's the only mechanism people had for adding tests.

Yeah I think we want to keep the external API the same. I reckon keep it as it is, but I'll stick some thoughts in another ticket for us to mull over for a later release.

Fixed the jshint error. Gonna pull this in since the whole repo is pretty much in dev mode. I think this works though, either way.