Timer.js

timer.js

function Timer(interval) {
    this.handlers = {};
    this.started = false;
    this.interval = interval;
};

Timer.prototype.tick = function () {
    if (!this.started) {
        return;
    }

    var self = this;

    this.id = setTimeout(function () {
        self.tick();
    }, this.interval);

    this.trigger('tick');
};

Timer.prototype.start = function () {
    if (this.started) {
        return;
    }

    this.started = true;
    this.trigger('start');
    this.tick();
};

Timer.prototype.stop = function () {
    this.started = false;
    clearInterval(this.id);
    this.trigger('stop');
};

Timer.prototype.on = function (ev, handler) {
    if (!this.handlers[ev]) {
        this.handlers[ev] = [];
    }

    this.handlers[ev].push(handler);
    return this;
}

Timer.prototype.trigger = function (ev) {
    if (!this.handlers[ev]) {
        return;
    }

    var handlers = this.handlers[ev];

    for (var i = 0, l = handlers.length; i < l; i++) {
        handlers[i].call(this);
    }


    return this;
}

Timer.prototype.onTick = function (handler) {
    return this.on('tick', handler);
};

Timer.prototype.onStart = function (handler) {
    return this.on('start', handler);
};

Timer.prototype.onStop = function (handler) {
    return this.on('stop', handler);
};



var t = new Timer(2000);
var i = 0;
t.onTick(function() {
    console.log(i++);
});

t.start();