or instead of a whole library use mozilla's compatibility when using bind... see the function here: https://developer.mozilla.org/en-US/docs/JavaScript/Referenc...

Because modifying object prototypes is the way to go?

Depends if you're in an environment you control then yes - when embedding your scripts, don't do it. Create your own isolated functions and assume anything and everything can be broken e.g. Array.prototype is often modified with broken or semi incomplete functions like broken versions of indexOf

How is this an improvement?

It looks basically equivalent but more confusing to me.

It's just a way of getting rid of the redundant "function()" syntax. Unfortunately with bind(), we have to set the scope even though it isn't always necessary. So in this case, the first parameter "this" is also probably redundant. The old PrototypeJS curry() would have been the least redundant solution: movePlayer.curry("north")

There's also partial():

1. http://documentcloud.github.io/underscore/#partial

It would be nice if they had called it curry() or at least created a curry() alias.

Nice, hadn't seen that before, looks like it was just added early this year.

If you use es5-shim (https://github.com/kriskowal/es5-shim), you can say movePlayer.bind(this, "north") on older browsers.