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JS 非图片动态loading效果实现代码

人气:0
代码如下:
首先实现该功能的js对象LoadingMsg:
复制代码 代码如下:

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
复制代码 代码如下:

var callObj = this;
this.intervalID = setInterval(function() { callObj.Loading(); }, this.timespan);

写成:
复制代码 代码如下:

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:
复制代码 代码如下:

<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
复制代码 代码如下:

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:
复制代码 代码如下:

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
复制代码 代码如下:

   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()。

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