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TIL: Stylesheets do not only block rendering but also JavaScript execution

stefanjudis profile image Stefan Judis Originally published at stefanjudis.com on ・1 min read

Today I learned that when you have the following snippet...

<link rel="stylesheet" href="app.css" />

<script>
  var script = document.createElement('script');
  script.src = "analytics.js";
  document.getElementsByTagName('head')[0].appendChild(script);
</script>

... the inline JavaScript code snippet won't be executed before the stylesheet is loaded. When you think about that, this makes a lot of sense because it may be that the JavaScript will access elements and any style-related values. I never thought about it, though.

All kudos to Harry Roberts who described this behavior in an excellent article. Thanks Harry!

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Stefan Judis

@stefanjudis

DevRel at Contentful. In love with web performance, new technologies, and accessibility – all the good stuff ✌️.

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