A small demonstrarion of a general curry function

curry_test.js

function curry(fn) {
  var slice = Array.prototype.slice;
  var arity = fn.length;
  var args  = slice.call(arguments, 1);

  function acc() {
    var largs = args;

    if (arguments.length > 0) {
      largs = largs.concat(slice.call(arguments, 0));
    }

    if(largs.length >= arity) {
      return fn.apply(this, largs);
    }
    else {
      return curry.apply(this, [fn].concat(largs));
    }
  };

  return args.length >= arity ? acc() : acc;
};

function add(a, b, c, d, e, f) {
  return a + b + c + d + e + f;
}

var curryAdd = curry(add);

console.log(curryAdd(1)(2)(3)(4)(5)(6) === add(1, 2, 3, 4, 5, 6)); // true
console.log(curryAdd(1)(2)(3)(4)(5)(6) === curryAdd(1, 2, 3, 4, 5, 6)); // true
console.log(curryAdd(1, 2)(3)(4)(5, 6) === curryAdd(1, 2, 3, 4)(5)(6)); // true
console.log(curryAdd(1)(2)(3, 4, 5, 6) === curryAdd(1, 2, 3, 4)(5)(6)); // true
// and so on...