A JavaScript implementation of curry.

curry.js

(function(){
    "use strict";

    /**
     * A factory for creating curry functions that 
     * are tied to the arrity of the function f.
     */
    function makeArrityBasedCurry(n) {
        var curry = function(f){
            var args = [].slice.call(arguments, 1);

            //Enforce f must be a function.
            if(typeof f !== "function"){
                throw new Error("f must be a function");
            }

            return function(){
                var largs = args.concat([].slice.call(arguments, 0));

                if(largs.length >= n){
                    return f.apply(this, largs);
                }else{
                    largs.unshift(f);
                    return curry.apply(this, largs);
                }
            };
        };
        return curry;
    }

    /**
     * Augment Function's prototype to support creating curried functions.
     */
    Function.prototype.curry = function(nParams){
        //If nParams is not provided ask "this" how many parameters it has.
        var arrity = nParams ? nParams : this.length;
        return makeArrityBasedCurry(arrity)(this);
    };

    /**
     * A function to be curried.
     * It is expecting 4 arguments when it is called.
     */
    var curry4 = function f(a, b, c, d) {
        return a + b + c + d;
    }.curry();

    /**
     * Make a curry whose target function f has an arity of 4.
     */
    var result;

    result = curry4(1)(2, 3, 4);
    console.log(result);
    
    result = curry4(1, 2)(3, 4);
    console.log(result);
    
    result = curry4(1, 2, 3)(4);
    console.log(result);
    
    result = curry4(1, 2, 3, 4);
    console.log(result);
    
    /// Since curry4 returns a function it can also be used as follows.
    
    result = curry4(1)(1)(1)(1);
    console.log(result);
}());