So, I'm following the Google PageSpeed recommendation to defer above-the-fold scripts. Let's say this is the code in my <head>:
<script src="/js/jquery.js"></script>
<script src="/js/functions.js"></script>
The functions.js script depends on jQuery so it's crucial that jquery.js is loaded and executed before functions.js.
What I tried:
defer
<script src="/js/jquery.js" defer></script>
<script src="/js/functions.js" defer></script>
While this works and functions.js gets executed properly, when I load the page I see it flicker, as if the CSS is not yet loaded. Note that the above code is in the <head>. If I remove the defer attribute from jquery.js, the flickering disappears. That leads me to my question:
Mixed
<script src="/js/jquery.js" async></script>
<script src="/js/functions.js" defer></script>
Does using async on the dependency script and defer on the dependent script ensure they will always be executed in that order? It seems to work in my tests but I don't know enough about how the parser works in order to be sure.
