Asynchronously loading script code_javascript skills

Asynchronously loading scripts through iframe
Asynchronously requesting scripts from another page will not be executed, and only the original HTML file will be returned, because the returned text has not been parsed and executed by the browser.
Look at the code
a1.html

Copy the code The code is as follows:

< ;html xmlns="http://www.w3.org/1999/xhtml">

a2.html

Copy code The code is as follows:

< ;html xmlns="http://www.w3.org/1999/xhtml">



<script> <br>alert('I am an asynchronous script'); <br></script>