A handful of reasons JavaScript won’t be available

1. A browser extension has interfered with the site
2. A spotty connection hasn’t loaded the dependencies correctly
3. Internal IT policy has blocked dependencies
4. WIFI network has blocked certain CDNs
5. A user is viewing your site on a train which has just gone into a tunnel
6. A device doesn’t have enough memory available
7. There’s an error in your JavaScript
8. An async fetch request wasn’t fenced off in a try catch and has failed
9. A user has a JavaScript toggle accidentally turned off
10. A user uses a JavaScript toggle to prevent ads loading
11. An ad blocker has blocked your JavaScript from loading
12. A user is using Opera Mini
13. A user has data saving turned on
14. Rogue, interfering scripts have been added by Google Tag manager
15. The browser has locked up trying to parse your JS bundle

That’s just a quick list of things I thought of on the top of my head. I could probably list off a bunch of others, but 15 items shows you how likely it is JavaScript will not be available, or available in a limited fashion.

Makes sense to build with progressive enhancement, right?

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Stuart Langridge made this really handy flow that does a great job of visualising all the problems that will happen.

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