Simple JavaScript Split Lap Timer

Timer.js

var Timer = (function(){

    now = Date.now || function () {return (new Date()).getTime();}

    var txt = function(len){return new Array(len).join().replace(/(.|$)/g, function(){return ((Math.random()*36)|0).toString(36);})}

    var STOP = 0;
    var START = 1;
    var PAUSE = 2;

    function Timer(name, key){
        this.name = name || txt(10);
        this.key = key || txt(10);

        _start = 0;
        _stop = 0;
        _total = 0;
        _status = 0; // STOP, START, PAUSE
        _laps = {};
    }

    Timer.prototype.start = function(){
        if (_status != START) {
            _start = now();
            if(_status == STOP)
            {
                _total = 0;
                _laps = {};
            }
            _status = START;
        }

        return this;
    };

    Timer.prototype.stop = function(){
        if (_status != STOP) {
            _stop = now();
            _status = STOP;
            _total += _stop - _start;
        }
        return this;
    };

    Timer.prototype.pause = function(){
        if (_status == START) {
            _stop = now();
            _status = PAUSE;
            _total += _stop - _start;
        }
        return this;
    };

    Timer.prototype.resume = function(){
        if (_status == PAUSE) {
            _status = START;
            _start = now();   
        }
        return this;
    }

    Timer.prototype.lap = function(name, key){
        if (_status == START){
            var tNow = now();
            key = key || txt(10);
            name = name || txt(10);

            _laps[key] = {
                name : name,
                key : key,
                saved : tNow,
                total : _total + tNow - _start
            };
        }
        return this;
        
    };

    Timer.prototype.laps = function(key){
        if (key){
            return _laps[key];
        }
        return _laps;
    }

    Timer.prototype.total = function(){
        if (_status == START) {
            return (_total + now() - _start);
        }
        return _total;
    };

    return Timer;

})();