stopwatch.js

var makeStopwatch = function() {
  var elapsed = 0;
  var interval;

  var stopwatch = function(){
    return elapsed;
  };

  var increase = function() { elapsed++; };

  return {
    start: function() { interval = setInterval(increase, 1000); },
    view: function() { return elapsed; },
    reset: function() { elapsed = 0; return "I'm reset!"; },
    stop: function() { clearTimeout(interval); }
  };
};

var myStopwatch = makeStopwatch();

myStopwatch.start();
myStopwatch.stop();
myStopwatch.reset();
myStopwatch.view();