倒计时

countDown.js

var countDown = (function($){
	var counts = {}, countTime, stopped = true, id = 0;

	function count(){
		var length = 0;
		$.each(counts, function(key, countObj){
			var timeObj, seconds = countObj.seconds - ((new Date().getTime() - countObj.startTime) /1000);

			if(seconds > 0){
				timeObj = {
					seconds: parseInt(seconds % 60, 10),
					minutes: parseInt((seconds / 60) % 60, 10),
					hours: parseInt((seconds / 60 / 60) % 24, 10),
					days: parseInt(seconds / 60 / 60 / 24, 10)
				};
				length++;
			}else{
				delete counts[key];
			}
			setTimeout(function(){countObj.callback(seconds, timeObj);}, 0);
		});

		if(length === 0){
			stop();
		}
	}

	function add(seconds, callback){
		var _id = 'count'+(id++);
		counts[_id] = {seconds: seconds, callback: callback, startTime: new Date().getTime()};
		start();
		return _id;
	}

	function stop(){
		window.clearInterval(countTime);
		stopped = true;
	}
	function start(){
		if(stopped){
			countTime = window.setInterval(count, 500);
			stopped = false;
		}
	}

	return {add: add, stop: stop, start: start};
})(jQuery);

countDown.add(200, function(seconds, timeObj){console.log('first:', seconds, timeObj);});
countDown.add(150, function(seconds, timeObj){console.log('second:', seconds, timeObj);});
countDown.add(100, function(seconds, timeObj){console.log('third:', seconds, timeObj);});