bind.coffee

unless Function::bind?
  Function::bind = (scope, args...) ->
    target = this
    if typeof target isnt "function" then throw new TypeError
    bound = ->
      unless this intanceof bound
        return target.apply scope, [args..., arguments...]
      F = ->
      F.prototype = target.prototype
      self = new F
      result = target.apply self, [args..., arguments...]
      return result if result is Object result
      self
    bound

bind.js

if(Function.prototype.bind == null) {
  Function.prototype.bind = function bind(scope) {
    var target = this;
    if (typeof target != "function") throw new TypeError();
    var args = [].slice.call(arguments, 1);
    var bound = function () {
      if (!(this instanceof bound)) {
        return target.apply(scope, [].concat.call(args, [].slice.call(arguments)));
      }
      var F = function(){};
      F.prototype = target.prototype;
      var self = new F;
      var result = target.apply(self, [].concat.call(args, [].slice.call(arguments)));
      if (Object(result) === result)
         return result;
      return self;
    };
    return bound;
  };
}

You can remove the result isnt null condition on line 12 of the CoffeeScript version, and result !== null on line 14 of the JavaScript version, unless it's for performance reasons.

It was pretty much just a direct port from the es5-shim version, so I left it. It probably was for performance. I'll remove it anyway. Thanks.