Can I just add "async" to make a script load asynchronously?

For example, I use Skimlinks on my website, and the code is:

<script type="text/javascript" src="//s.skimresources.com/js/67963X1515853.skimlinks.js"></script>

Code (markup):

Can I just change that to the following to make it load asynchronously, and will it still work to affiliate links?

<script type="text/javascript" src="//s.skimresources.com/js/67963X1515853.skimlinks.js async"></script>

Code (markup):

If so, would the same work for my Amazon CPM ads? For example, I could change this?

<script type="text/javascript" language="javascript" src="//c.amazon-adsystem.com/aax2/getads.js"></script>
<script type="text/javascript" language="javascript">
//<![CDATA[
aax_getad_mpb({
  "size":"300x250",
  "slot_uuid":"15147327-1f46-48c3-ba92-6a152603cd8b"
});
//]]>
</script>

Code (markup):

(adding two instances of "async") to this?

<script type="text/javascript" language="javascript" src="//c.amazon-adsystem.com/aax2/getads.js" async></script>
<script type="text/javascript" language="javascript" async>
//<![CDATA[
aax_getad_mpb({
  "size":"300x250",
  "slot_uuid":"15147327-1f46-48c3-ba92-6a152603cd8b"
});
//]]>
</script>

Code (markup):

 

You can only use asnyc when you don't depend on that particular script further down in your code. The example you showed won't work, since the first script will get loaded asynchronously, and your code will run immediately after that, which would cause an error, since the first script isn't loaded yet.

You can only use async for javascript files which are independent.

 

Got it. Thanks!