Async script execution order

Question

The spec states "Scripts with async execute in the load-first order. Their document order doesn’t matter – which loads first runs first".

I've also read that async scripts should be completely independent.

In this scenario, is there no guarantee that non-async-script will be loaded before the async script loads?

<script src="non-async-script.js"></script>
<script src="async-script.js" async></script>

If you are still wondering if you can control the load order, I will shameless drop you this link: github.com/IbrahimTanyalcin/taskq — ibrahim tanyalcin
– ibrahim tanyalcin, Commented Jul 27, 2018 at 17:59

Alexander O'Mara · Accepted Answer · 2017-07-11 02:24:03Z

2

Historically, browsers would stop parsing the DOM until after the script tag is loaded.

Modern browsers do roughly the same thing, but to load resources in parallel it will read ahead in the DOM to find upcoming requests.

So to answer your question, the first script tag is not guaranteed to load before the second script, but it should execute before before the async script.

answered Jul 11, 2017 at 2:24

Alexander O'Mara

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