curry.js

var curry = (function () {
 
  var makeFn = function (fn, arity, reverse, prevArgs) {
    return function () {
      var newArgs = Array.prototype.slice.call(arguments, 0),
          args    = prevArgs.concat(newArgs);
      if (args.length < arity) {
        return makeFn(fn, arity, reverse, args);
      } else {
        return fn.apply(null, reverse ? args.reverse() : args);
      }
    };
  };
 
  return function (fn, arity, reverse) {
    if (typeof arity === "undefined") {
      arity = fn.length;
    }
    return makeFn(fn, arity, reverse, []);
  };
 
}).call(null);

Function.prototype.c = function (arity, reverse) {
  return curry(this, arity, reverse);
};

examples.js

// Examples

var foo = function (a, b, c) { return a + b + c }.c();

foo(1)()(1, 1) // => 3
foo(2)(2)(2)   // => 6
foo()()()()(1) // => [Function]

// first parameter overrides the function arity (number of parameters)
var max3 = Math.max.c(3);

max3(1, 2, 3)  // => 3
max3(1)(3)(10) // => 10

// second parameter reverses the parameters before applying
var delay = setTimeout.c(2, true)(1000);

delay(function () {
  console.log("this will run after 1 second");
});

// curry is basically a better way of doing what Function.prototype.bind does
var add = function (x, y) { return x + y; };
var add10 = add.bind(null, 10);

add10(20) // => 30

// same thing with currying
var add = function (x, y) { return x + y }.c();
var add10 = add(10);

add10(40) // => 50