How to ensure the execution order of JavaScript: jQuery.html is not *

How to ensure the execution order of JavaScript: jQuery.html is not *_jquery

WBOY

Release： 2016-05-16 18:10:01

Original

1147 people have browsed it

1. Introduction
In the previous article "How to ensure the execution order of JavaScript - In-depth analysis of jQuery.html", we revealed the reason why the jQuery.html function can be used in various browsers The secret to keeping dynamic JS executing sequentially is – synchronous AJAX retrieval of external JavaScript.
Let’s briefly review the HTML source code (test2.htm):

Copy the code The code is as follows:

< ;/div>

By the way, external JavaScript loaded in this way cannot be debugged in Firebug, Because after AJAX ends, the parsing of external JavaScript and the parsing of inline JavaScript are the same (both call jQuery.globalEval):

Let’s get to the topic of this article: If the loaded JS is in another domain, can jQuery.html still guarantee the sequential execution of JS in each browser?
2. Create a test case
1) Prepare two domain names
For testing, I temporarily created two subdomains under my personal homepage (http://sanshi.me/) , respectively:
http://test.sanshi.me/
http://test1.sanshi.me/
2) Update the Demo page (test2_1.htm)
I will add test2_1 .htm is placed under the first subdomain name, and the access address is http://test.sanshi.me/jsorder/test2_1.htm. Its source code is as follows:

Copy the code The code is as follows:

< ;script src="js/jquery-1.4.4.js" type="text/javascript"> 
<script> <br>$(function () { <br>$( '#container').html('<script src="http://test1.sanshi.me/jsorder/service.ashx?file=js/jquery-ui.js&delay=2000" type="text/javascript" ></script>' '<script>alert(typeof(jQuery.ui));</script>'); 
}); 

< /head>

可以看到，其中的jQueryUI脚本指向的是第二个域名下的（test1.sanshi.me）。
3) 在不同浏览器下测试

	test2_1.htm 使用jQuery.html函数动态加载其它域下的JavaScript
Firefox 3.6
IE 8
Chrome 10
Safari 4
Opera 11

3. jQuery.html并非万能钥匙，那么
不知道大家是否还记得我们在第一篇文章中提到的test3.htm不，这个结果和那个示例的结果一模一样，jQuery.html也并非万能钥匙。这不禁让我们怀疑这两个示例的内部逻辑是否一样？
但是第二篇文章不是明明白白告诉我们，jQuery.html使用的是同步AJAX的机制来加载外部JS的么？等等。。。。。。
大家有没有从上面的分析中发现问题，AJAX来加载其他域的资源，这不是明摆着违背了大名鼎鼎的同源策略（Same Origin Policy）了么？所以jQuery不可能这么实现，我们来看看jQuery.ajax文档是怎么说的：