Stop Watch

stopwatch.js

window.StopWatch = (function() {

    var seconds = 0;

    var minutes = 0;

    var timer = null;

    var events = {
        second: [],
        minute: []
    };

    var emit = function(event, value) {
        for (var i = 0, len = events[event].length; i < len; i++) {
            events[event][i].call(this, value);
        }
    };

    function StopWatch(cfg) {
        cfg = cfg || {};
        if (cfg.autostart) {
          this.start();
        }
    }

    StopWatch.prototype.on = function(event, callback) {
        if (events[event]) {
            events[event].push(callback);
        }

        return this;
    };

    StopWatch.prototype.stop = function() {
        clearInterval(timer);
        timer = null;
    };

    StopWatch.prototype.start = function() {
        if (timer === null) {
            (function(that) {
                timer = setInterval(function() {
                    seconds++;
                    if (seconds === 60) {
                        seconds = 0;
                        minutes++;
                        emit.call(that, 'minute', minutes);
                    }
                    emit.call(that, 'second', seconds);
                }, 1000);
            })(this);
        }
    };

    StopWatch.prototype.reset = function() {
        this.stop();
        seconds = 0;
        minutes = 0;
        emit('second', seconds);
        emit('minute', minutes);
    };

    return StopWatch;

})();