Uses variable-length arguments and closures to create an adding adding function

add.js

// H5BP Front-end Developer Interview Questions
// https://github.com/h5bp/Front-end-Developer-Interview-Questions#jscode
// Usage:
//  1 = add(1)();
//  3 = add(1, 2)();
//  6 = add(1, 2)(3);
// 10 = add(1, 2)(3, 4);
//  0 = add()();

var add = function () {
    var first = 0;
    for (var i = 0; i < arguments.length; i++) {
        first += arguments[i];
    }
    return function () {
        var second = 0;
        for (var i = 0; i < arguments.length; i++) {
            second += arguments[i];
        }
        return first + second;
    }
}