original from http://ejohn.org/blog/partial-functions-in-javascript/

gistfile1.js

Function.prototype.partial = (function(slice, undefined) {
  return function() {
    var fn = this, args = slice.call(arguments);
    return function() {
      var arg = 0, index, length = arguments.length;
      while (((index = args.indexOf(undefined)) > -1) && (index < length)) {
        args.splice(index, 1, arguments[arg++]);
      }
      return fn.apply(this, args);
    };
  };
})(Array.prototype.slice);