功能说明:譬如在按某个button时,显示消息"Loading”,然后每隔一秒后后面加上".",至一定数量的"."时如:"Loading...",再重置此消息为"Loading",继续动态显示,直至按钮事件处理完成。
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()。