[jsbin.com demo](http://jsbin.com/IgaXEVI/167/edit)

您会看到演示代码只是一个开始/停止/重置毫秒计数器。如果您想按时进行奇特的格式化，那完全取决于您。这应该足以让您入门。

这是一个有趣的小项目。这是我的处理方式

var Stopwatch = function(elem, options) {

  var timer       = createTimer(),
      startButton = createButton("start", start),
      stopButton  = createButton("stop", stop),
      resetButton = createButton("reset", reset),
      offset,
      clock,
      interval;

  // default options
  options = options || {};
  options.delay = options.delay || 1;

  // append elements     
  elem.appendChild(timer);
  elem.appendChild(startButton);
  elem.appendChild(stopButton);
  elem.appendChild(resetButton);

  // initialize
  reset();

  // private functions
  function createTimer() {
    return document.createElement("span");
  }

  function createButton(action, handler) {
    var a = document.createElement("a");
    a.href = "#" + action;
    a.innerHTML = action;
    a.addEventListener("click", function(event) {
      handler();
      event.preventDefault();
    });
    return a;
  }

  function start() {
    if (!interval) {
      offset   = Date.now();
      interval = setInterval(update, options.delay);
    }
  }

  function stop() {
    if (interval) {
      clearInterval(interval);
      interval = null;
    }
  }

  function reset() {
    clock = 0;
    render();
  }

  function update() {
    clock += delta();
    render();
  }

  function render() {
    timer.innerHTML = clock/1000; 
  }

  function delta() {
    var now = Date.now(),
        d   = now - offset;

    offset = now;
    return d;
  }

  // public API
  this.start  = start;
  this.stop   = stop;
  this.reset  = reset;
};

获取一些基本的HTML包装器

<!-- create 3 stopwatches -->
<div class="stopwatch"></div>
<div class="stopwatch"></div>
<div class="stopwatch"></div>

从那里开始使用就变得很简单

var elems = document.getElementsByClassName("stopwatch");

for (var i=0, len=elems.length; i<len; i++) {
  new Stopwatch(elems[i]);
}

另外，您还可以获得计时器的可编程API。这是一个用法示例

var elem = document.getElementById("my-stopwatch");
var timer = new Stopwatch(elem, {delay: 10});

// start the timer
timer.start();

// stop the timer
timer.stop();

// reset the timer
timer.reset();

jQuery插件

至于jQuery部分，一旦您拥有了上述不错的代码组成，编写jQuery插件就很容易了

(function($) {

  var Stopwatch = function(elem, options) {
    // code from above...
  };

  $.fn.stopwatch = function(options) {
    return this.each(function(idx, elem) {
      new Stopwatch(elem, options);
    });
  };
})(jQuery);

jQuery插件用法

// all elements with class .stopwatch; default delay (1 ms)
$(".stopwatch").stopwatch();

// a specific element with id #my-stopwatch; custom delay (10 ms)
$("#my-stopwatch").stopwatch({delay: 10});