jashkenas/underscore — pull request #1936 by jridgewell (2014-11-14 20:39:06+00:00)
Title: Optimize isFunction only when appropriate.

Closes #1929.

@jdalton: How did you test this? Seems PhantomJS doesn't play nicely with `typeof` or `toString.call` (returning `object` and `[object Int8ArrayConstructor]`).