javascript - <script defer> not working as expected - Stack Overflow

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I am trying to defer my script execution because it is not important that it executes before the page is rendered. However, it is not working as I understand it.

According to this article (and others like it), if I use defer then the execution order is preserved. However, when using highlight.js I am seeing a different behaviour. My script files look like so:-

<script defer type="text/javascript" src="//cdnjs.cloudflare/ajax/libs/highlight.js/8.7/highlight.min.js"></script>
<script defer type="text/javascript">hljs.initHighlightingOnLoad();</script>

Now as I understand it they should execute in order which is unlike the behaviour of async. However, I get the following error in Chrome (version 44.0.2403.157).

If I remove the defer attributes it works as expected. What am I not understanding correctly?

I am trying to defer my script execution because it is not important that it executes before the page is rendered. However, it is not working as I understand it.

According to this article (and others like it), if I use defer then the execution order is preserved. However, when using highlight.js I am seeing a different behaviour. My script files look like so:-

<script defer type="text/javascript" src="//cdnjs.cloudflare./ajax/libs/highlight.js/8.7/highlight.min.js"></script>
<script defer type="text/javascript">hljs.initHighlightingOnLoad();</script>

Now as I understand it they should execute in order which is unlike the behaviour of async. However, I get the following error in Chrome (version 44.0.2403.157).

If I remove the defer attributes it works as expected. What am I not understanding correctly?

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Share Improve this question Follow edited Feb 8, 2017 at 15:05 CommunityBot 111 silver badge asked Aug 26, 2015 at 11:38 baynezybaynezy 7,0761212 gold badges5555 silver badges8181 bronze badges 1

• 1 wouldnt this only work if hljs.initHighlightingOnLoad() was also in an external file (and the loading of that file was "defer'd")? – atmd Commented Aug 26, 2015 at 11:43

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1 Answer 1

Sorted by: Reset to default 6

The defer attribute has been browser specific http://caniuse./#feat=script-defer (thanks to atmd)

The defer and async attributes must not be specified if the src attribute is not present.

Check your second case.

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