What is the difference between:
<link rel="preload" as="script" href="..">
and
<script src="..." />
Is rel="preload" really needed in the first example?
The first one asks the browser to download a script, but not execute it.
In case it is requested somehow, the browser can simply load it from cache.
The second one downloads a script and executes its content.
If you use link, you need to fill rel as preload. You can't embed js via link.
With link you ask the browser to cache something, because you might need it soon.