Add ASYNC to <script> tag on when running document.head

Question

I'm trying to inject a JavaScript file into <head></head>. The JavaScript file is async, and I want to add it to the script tag when injecting.

This is what I have so far:

var imported = document.createElement('script');
imported.src = 'http://domain/js/my.js';
imported.setAttribute("type", "text/javascript");
imported.async = async;
document.head.appendChild(imported);

This injects the JavaScript file, but I get error on line imported.async = async;:

uncaught ReferenceError: async is not defined

And async is not added to the tag.

How can I add async into that injected JavaScript file?

PS: I'm not looking for a jQuery answer, only pure JavaScript.

async is not defined in your script.. Either define it or just imported.async = true; — Rayon
– Rayon, Commented Oct 19, 2016 at 17:21
Possible duplicate of Create script tag with async attribute — Heretic Monkey
– Heretic Monkey, Commented Oct 19, 2016 at 17:22
@PriyeshKumar Thanks, imported.async = true is correct. Add it as a answer and I can check it as correct — Rubioli
– Rubioli, Commented Oct 19, 2016 at 17:24
@MikeMcCaughan Thats with jQuery and I look for a pure javascript — Rubioli
– Rubioli, Commented Oct 19, 2016 at 17:24

Priyesh Kumar · Accepted Answer · 2016-10-19 17:40:18Z

5

async variable is not defined and so imported.async = async; will throw error.

You can do var async = true; or false and then imported.async = async;

OR

imported.async = true;

Note that async attribute should be boolean.

Read docs: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script

answered Oct 19, 2016 at 17:40

Priyesh Kumar

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Daniël van der Burgt · Accepted Answer · 2018-11-11 03:11:09Z

0

I can not comment.. because I don't have the rep. But I wanted to add to the accepted answer, that you could also have done:

imported.async = !!async;

this would asign false if the value is false or if async is undefined and true only if defined and initialized on true.

answered Nov 11, 2018 at 3:11

Daniël van der Burgt

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