A JavaScript implementation of partial.

partial.js

(function(){
    "use strict";

    /**
     * Creating a partial the hard way.
     */
    (function(){

        function add(x){
            return function(y){
                return x + y;
            };
        }

        /// Using the above partial to add numbers.
        var add1 = add(1);
        var result = add1(10);
        console.log(result);

        /// Using the above partial to concatenate strings.
        var greet = add("Hello, ");
        var greeting = greet("Mr Bojangles");
        console.log(greeting);
        
    }());

    /** 
     * Creating a partial using a partial factory.
     */
    (function(){

        function add(a, b){
            return a + b; 
        }

        function partial(func, x){
            if(typeof func !== "function") { 
                throw new Error("func must be a function");
            }
            return function(y){
                return func(x, y);
            };
        }

        var add1 = partial(add, 1);
        var result = add1(1);
        console.log(result);
        
    }());

    /**
     * You can even create a partial for a function that accepts more than 2 argument.
     */
    (function(){

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

        function partial(func) {
            if(typeof func !== "function") {
                throw new Error("func must be a function");
            }
            var args = [].slice.call(arguments, 1);
            return function(y){
                args.push(y);
                return func.apply(undefined, args);
            };
        }

        var addFiveValues = partial(addFive, 2, 3, 4, 5);
        var addFiveMoreValues = partial(addFive, 12, 13, 14, 15);
        var addSomeLetters = partial(addFive, "a,", "b,", "c,", "d,");
        var result = addFiveValues(10); // ==> 10
        console.log(result);
        result = addFiveMoreValues(11); // ==> 65
        console.log(result);
        result = addSomeLetters("e"); // ==> 65
        console.log(result);
        
    }());

}());