A cute currying function written in pure JavaScript for FUNZIES.

curry.js

var curry = function (f, args, binding) {
  if (typeof f !== 'function' ||
      toString.call(args) !== '[object Array]') {
    throw new Error('Invalid parameters');
    return;
  }

  if (typeof binding !== 'object') {
    binding = this;
  }

  return function () {
    var _args = args.concat(Array.prototype.slice.call(arguments));
    return f.apply(binding, _args);
  };
};

// Example usage

var add = function(x, y, z) {
  return x + y + z;
};

var addTwo = curry(add, [2]);

console.log(addTwo(4, 6)); // 12
console.log(addTwo(1, 3)); // 6

var addTwoAndFour = curry(add, [2, 4]);

console.log(addTwoAndFour(6)); // 12 as well!

made a final edit with some of your suggestions/hints