Parallel JS

parallel.js

function Parallel() {
    var self = this;
    self.finished = 0;
    self.length = 0;
    self.list = [];

    self.add = function (fn, context, params) {
        params = params || [];
        context = context || this;
        self.list.push({fn: fn, params: params, context: context});
        self.length++;
    };

    function callback() {
        self.finished++;
        if (self.finished == self.length) {
            self.final();
        }
    }

    self.start = function (cb) {
        self.final = cb;
        if (self.list.length){
            self.list.forEach(function (item) {
                var args = item.params;
                args.push(callback);
                item.fn.apply(item.context, args);
            });
        } else {
            cb();
        }
    }
}