JavaScript脚本动态脚本加载IE6问题

Question

I am using an in house custom library to replicate jsonp calls. Before you guys ask me to use JQuery or other libraries, let me tell I cannot use it due to some constraints.

Below is the code used to make the request:

 BurrpJsonAjaxRequest.prototype.send = function() { this.script = document.createElement("script"); this.script.type = "text/javascript"; this.script.charset = "UTF-8"; this.script.src = this.URL; if (typeof(this.callBack) == "function") { this.script.callback = this.callBack; } var currRequest = this; //sleep(100); if (this.script.src.readyState) { //IE this.script.src.onreadystatechange = function() { if (this.script.src.readyState == "loaded" || this.script.src.readyState == "complete") { this.script.src.onreadystatechange = null; currRequest.hideLoading(); currRequest.callback(); } }; } else { //Others this.script.src.onload = function() { currRequest.hideLoading(); currRequest.callback(); }; } this.docHead.appendChild(this.script); }; 

This works the first time it is executed. On subsequent executions, the request is made but the callback is not executed.

If I use a sleep method(commented in the code) as below, the callback gets executed on subsequent calls also.

 function sleep(milliseconds) { var start = new Date().getTime(); for (var i = 0; i milliseconds){ break; } } } 

How does the sleep influence the execution of the call back? Works fine in Firefox though.

Answer 1

First time through, this.script.src.readyState is false (script still loading) and a handler is created for the onLoad event. When onLoad is triggered, the anonymous onLoad function is called - which appears to be very similar to the onReadyStateChange handler. However, onLoad is triggered only once, so your function is called only once.

The sleep slows execution enuf so your this.script.src.readyState is true when you execute the if statement.

What do you think?