SOURCE

function happy() {
    var sum = 0
    console.log(arguments)
    var a = arguments.length
    for (var i = 0; i < a; i++) {
        sum += arguments[i]
    }
    var kksk = function () {
        console.log(arguments)
        if (arguments.length == 0) {
            console.log(sum)
        }
        else {
            var a = arguments.length
            for (var i = 0; i < a; i++) {
                sum += arguments[i]
            }
            console.log(sum)
        }
        return kksk;
    }
    return kksk
}
happy(1, 2, 3)(1,2)(1,2,3)(1,2,3,4,5,6,7)