stopwatch.js

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

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

    var stopInterval = function() {
        clearInterval(intervalId);
    };

    return {
        start: function() { intervalId = setInterval(increase, 1000); },
        view: function() { return elapsed; },
        pause: stopInterval,
        reset: function() {
            elapsed = 0;
            stopInterval();
            return "I'm reset!";
        }
    };
};

var myStopwatch = makeStopwatch();

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