Why doesn't defer work?

Question

JavaScript

Async.js is included on the page :

<script type="text/javascript" src="async.js" async></script>

async.js content :

var script = document.createElement("script");

script.src = "defer.js";
script.defer = true;
script.type = "text/javascript";

document.head.appendChild(script);

But defer.js is not executed after the page is loaded, but as if it had an async attribute, instead of defer . (If you open the debugger, then the DOM node will be there without async, namely with defer ).
Why?

Answer 1

For the advanced reader who knows that tags <script>can be added to a page at any time using javascript itself, note that scripts added this way behave just like async. That is, they are executed as soon as they are loaded, without preserving the relative order.
If you need to preserve the order of execution, that is, add several scripts that will be executed strictly one after the other, then the script.async = false property is used.

https://learn.javascript.ru/external-script#async...