Autocurry.js

Function.prototype.ac = (function(){
  return ac;
  function ac(len, bind, args){
    var func = this
      , args = args || [];
    return function internal(){
      args = args.concat(Array.prototype.slice.call(arguments));
      len -= arguments.length;
      if (len > 0) return internal;
      else func.apply(bind, args);
    };
  };
})();

(function(a, b, c, d){
  console.log(a + b + c + d);
}).ac(4)(1)(2)(3)(4);