ok,不废话了，实现一个javascript的Timer吧
比起as3的Timer类，功能上略有改动
timer2.src.js
复制代码 代码如下:
/**
* Timer 模型
*
* @author rainsilence
* @version 2.0
*/
(function() {
/**
* TimerEvent constructor 构造器
*
* @param type 事件类型
* @param bubbles 是否毛票
* @param cancelable 是否可取消
*/
TimerEvent = function(type, bubbles, cancelable) {
this.type = type;
this.bubbles = bubbles;
this.cancelable = cancelable;
};
/**
* Event 时间事件声明
*
* @event TIMER
* @event TIMER_COMPLETE
*/
extend(TimerEvent, {
TIMER : "timer",
TIMER_COMPLETE : "timerComplete"
});
/**
* Event 方法
*
* @method toString
*/
extend(TimerEvent.prototype, {
toString : function() {
return "[TimerEvent type=" + this.type +
" bubbles=" + this.bubbles +
" cancelable=" + this.cancelable +"]";
}
});
/**
* Extend 扩展类，对象的属性或者方法
*
* @param target 目标对象
* @param methods 这里改成param也许更合适，表示承载着对象，方法的对象，用于target的扩展
*/
function extend(target, methods) {
if (!target) {
target = {};
}
for (var prop in methods) {
target[prop] = methods[prop];
}
return target;
}
/**
* Timer 构造器
*
* @param delay 延时多少时间执行方法句柄
* @param repeatCount 重复多少次，如果不设置，代表重复无限次
*/
Timer = function(delay, repeatCount) {
var listenerMap = {};
listenerMap[TimerEvent.TIMER] = [];
listenerMap[TimerEvent.TIMER_COMPLETE] = [];
extend(this, {
currentCount : 0,
running : false,
delay : delay,
repeatCount : repeatCount,
// true:Interval,false:Timeout
repeatType : repeatCount == null || repeatCount < 1 ? true : false,
handler : listenerMap,
timerId : 0,
isCompleted : false
});
};
// 事件对象初始化（这部分未实现）
var timerEvent = new TimerEvent(TimerEvent.TIMER, false, false);
var timerCompleteEvent = new TimerEvent(TimerEvent.TIMER_COMPLETE, false, false);
/**
* Timer 计时器方法
*
* @method addEventListener 增加一个方法句柄（前两个参数必须，后一个参数可选）
* @method removeEventListener 移除一个方法句柄
* @method start 开始计时器
* @method stop 结束计时器
* @method reset 重置计时器
*/
extend(Timer.prototype, {
addEventListener : function(type, listener, useCapture) {
if (type == TimerEvent.TIMER || type == TimerEvent.TIMER_COMPLETE) {
if (!listener) {
alert("Listener is null");
}
if (useCapture == true) {
this.handler[type].splice(0, 0, [listener]);
} else {
this.handler[type].push(listener);
}
}
},
removeEventListener : function(type, listener) {
if (type == TimerEvent.TIMER || type == TimerEvent.TIMER_COMPLETE) {
if (!listener) {
this.handler[type] = [];
} else {
var listeners = this.handler[type];
for (var index = 0; index < listeners.length; index++) {
if (listeners[index] == listener) {
listeners.splice(index, 1);
break;
}
}
}
}
},
start : function() {
var timerThis = this;
if (this.running == true || this.isCompleted) {
return;
}
if (this.handler[TimerEvent.TIMER].length == 0 &&
this.handler[TimerEvent.TIMER_COMPLETE].length == 0) {
alert("No Function");
return;
}
if (this.repeatType) {
this.timerId = setInterval(function() {
dispachListener(timerThis.handler[TimerEvent.TIMER], timerEvent);
timerThis.currentCount++;
}, this.delay);
} else {
this.timerId = setTimeout(function() {delayExecute(timerThis.handler[TimerEvent.TIMER]);}, this.delay);
}
this.running = true;
function delayExecute(listeners) {
dispachListener(listeners, timerEvent);
timerThis.currentCount++;
if (timerThis.currentCount < timerThis.repeatCount) {
if (timerThis.running) {
timerThis.timerId = setTimeout(function() {delayExecute(listeners);}, timerThis.delay);
}
} else {
timerThis.running = false;
}
if (timerThis.running == false) {
if (!timerThis.isCompleted) {
dispachListener(timerThis.handler[TimerEvent.TIMER_COMPLETE], timerCompleteEvent);
}
timerThis.isCompleted = true;
}
}
function dispachListener(listeners, event) {
for (var prop in listeners) {
listeners[prop](event);
}
}
},
stop : function() {
this.running = false;
if (this.timerId == null) {
return;
}
if (this.repeatType) {
clearInterval(this.timerId);
} else {
clearTimeout(this.timerId);
}
if (!this.isCompleted) {
var listeners = this.handler[TimerEvent.TIMER_COMPLETE];
for (var prop in listeners) {
listeners[prop](timerCompleteEvent);
}
}
this.isCompleted = true;
},
reset : function() {
this.currentCount = 0;
this.isCompleted = false;
}
});
})();

接下来测试吧，大家见过新浪网上的滚动显示吗？用setTimeout写的，真叫牛叉。。。。。。换成Timer重构，简单易懂
timerTest.html
复制代码 代码如下:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-31j">
<title>Insert title here</title>
<style type="text/css">
.rowLine {
width: 400px;
height: 80px;
border-bottom-style: solid;
border-width: 1px;
}
.barList {
border-style: solid;
border-width: 1px;
width:400px;
height: 80px;
overflow: hidden;
}
</style>
<script type="text/javascript" src="/UploadFiles/2021-04-02/timer2.src.js"><script type="text/javascript">
<!--
var timer = new Timer(50);
var globalTimer = new Timer(10000);
var bList;
function init() {
bList = document.getElementById("barList");
timer.addEventListener(TimerEvent.TIMER, calTime);
timer.start();
globalTimer.addEventListener(TimerEvent.TIMER, controlTime);
globalTimer.start();
}
function controlTime() {
if (!timer.running) {
timer.reset();
timer.start();
}
}
function calTime() {
bList.scrollTop += 1;
if (bList.scrollTop > 80) {
timer.stop();
var barNode = bList.firstChild;
if (barNode.nodeType == 3) {
bList.appendChild(barNode);
bList.appendChild(bList.getElementsByTagName("div")[0]);
} else {
bList.appendChild(barNode);
}
bList.scrollTop = 0;
}
}
window.onload = init;
// -->
</script>
</head>
<body>
<div class="barList" id="barList">
<div class="rowLine" style="background-color: red" style="background-color: red">1</div>
<div class="rowLine" style="background-color: pink" style="background-color: pink">2</div>
<div class="rowLine" style="background-color: blue" style="background-color: blue">3</div>
<div class="rowLine" style="background-color: gray" style="background-color: gray">4</div>
</div>
</body>
</html>

addEventListener的useCapture参数本为捕获阶段触发之意，现在改成如果true,则在其他句柄之前触发，如果false，则在其他句柄之后触发。
后记：
现在貌似大家比较流行评论说明书的用法。。。比如struts+spring+hibernate。而忽略了编程的实质。希望大家多看源码，多讨论源码，那样才会有所谓的思想。否则人家今天用这个framework，明天换了。你又要从头开始了。