Counter.js

function Counter(start) {
    var count = start;
    var timer;
    var timerDelay = 1000;
    return {
      increment: function(){
        count++;
      },
      start: function(){
        if(timer == undefined){
          timer = setInterval(function(){
            this.increment();
            console.log('count:' + count);
          }.bind(this),timerDelay);
        }
      },
      stop: function(){
        clearInterval(timer);
        timer = undefined;
      },
      get: function() {
        return count;
      }
    }
}
var c = Counter(0);