[javascript patterns] Function binding

gistfile1.js

if ( !Function.prototype.bind ) {
  Function.prototype.bind = function( obj ) {
    var slice = Array.prototype.slice,
        args = slice.call(arguments, 1),
        self = this,
        nop = function () {},
        bound = function () {
          return self.apply( this instanceof nop ? this : ( obj || {} ),
          args.concat( slice.call(arguments) ) );
        };
    nop.prototype = self.prototype;
    bound.prototype = new nop();
    return bound;
  };
}