代码如下：
首先实现该功能的js对象LoadingMsg：
var Class = {
create: function() {
return function() { this.init.apply(this,arguments); }
}
}
var LoadingMsg = Class.create();
LoadingMsg.prototype = {
init: function(spanId, spanMsg) {
this.intervalID = -10000;
this.spanId = spanId;
this.spanMsg = spanMsg;
this.timespan = 1000;
this.pointNum = 3;
this.initPointMsg = "...";
},
Loading: function() {
var maxLength = this.spanMsg.length + this.pointNum;
var currentSpanMsg = document.getElementById(this.spanId).innerHTML;
if (currentSpanMsg.length < maxLength) {
document.getElementById(this.spanId).innerHTML += ".";
}
else {
document.getElementById(this.spanId).innerHTML = this.spanMsg;
}
},
Start: function() {
document.getElementById(this.spanId).innerHTML = this.spanMsg + this.initPointMsg;
var callObj = this;
this.intervalID = setInterval(function() { callObj.Loading(); }, this.timespan);
},
End: function() {
document.getElementById(this.spanId).innerHTML = "";
clearInterval(this.intervalID);
}
}
关键点：
如果把
var callObj = this;
this.intervalID = setInterval(function() { callObj.Loading(); }, this.timespan);
写成：
this.intervalID = setInterval(this.Loading, this.timespan);
在执行Loading方法时则会报找不到this.spanMsg的错误。
因为在setInterval里的第一个参数里的this是windows对象，而不是LoadingMsg对象。windows.setInterval嘛。
应用该方法：
<body>
<input type="button" value="Start" onclick="javascript:StartLoading();" />
<span id="spanId" style="color:Red"></span>
<br />
<input type="button" value="End" onclick="javascript:EndLoading();" />
<br /><br />
<script type="text/javascript">
var loadingMsgObj = new LoadingMsg("spanId","loading");
function StartLoading() {
loadingMsgObj.Start();
}
function EndLoading() {
loadingMsgObj.End();
}
</script>
</body>
来源于prototype.js里经典创建Js对象的
var Class = {
create: function() {
return function() { this.init.apply(this,arguments); }
}
}
var LoadingMsg = Class.create();
在Class.create()的时候做了2件事，1个是创建了LoadingMsg的对象，即var LoadingMsg = function() {}；
另外一件事就是调用LoadingMsg的init方法，初始化LoadingMsg里的静态私有变量，相当于c#里的构造函数作用。
如果你觉得这很装逼的话，如果你更喜欢简单朴实的女孩子的话，也可以改写LoadingMsg对象：
var LoadingMsg = function() { };
LoadingMsg.prototype = {
init: function(spanId, spanMsg) {
this.intervalID = -10000;
this.spanId = spanId;
this.spanMsg = spanMsg;
this.timespan = 1000;
this.pointNum = 3;
this.initPointMsg = "...";
},
Loading: function() {
var maxLength = this.spanMsg.length + this.pointNum;
var currentSpanMsg = document.getElementById(this.spanId).innerHTML;
if (currentSpanMsg.length < maxLength) {
document.getElementById(this.spanId).innerHTML += ".";
}
else {
document.getElementById(this.spanId).innerHTML = this.spanMsg;
}
},
Start: function(spanId, spanMsg) {
this.init(spanId, spanMsg);
document.getElementById(this.spanId).innerHTML = this.spanMsg + this.initPointMsg;
var callObj = this;
this.intervalID = setInterval(function() { callObj.Loading(); }, this.timespan);
},
End: function() {
document.getElementById(this.spanId).innerHTML = "";
clearInterval(this.intervalID);
}
}
所不同的是把init的过程调到Start时执行，因此调用的时候也就变成了
var loadingMsgObj = new LoadingMsg();
function StartLoading() {
loadingMsgObj.Start("spanId", "loading");
}
从面向对象的习惯上来说，我个人还是倾向第一种写法，在实例化对象的时候即传入参数，而不是执行对象方法的时候传入参数。
另外关于setInterval方法传参数时，如果参数是简单的string，可以
setInterval("DisplayXYZ('xyz')",1000);
如果参数是对象，
则可以setInterval(function(){DisplayXYZ(obj);},1000);
LoadingMsg还是主要用在Ajax中，应用于执行时间可能较长的场景，在发送请求后loadingMsgObj.Start()，在成功获取响应时loadingMsgObj.End()。