The <noscript> element as a trap

One of the few traps of the web is how the <noscript> element doesn't provides the right behavior.

Definition: The <noscript> element provides alternate content when JavaScript is entirely toggled off or entirely unsupported.
Sources:

• HTML4 § 18.3.1 The NOSCRIPT element with ignoring non-JavaScript in <script> (W3C gives Tcl as example, I'd more point to JScript and VBScript, both of which are thankfully gone)
• WHATWG HTML (multipage) § The noscript element

While the way to obtain the right behavior is to have a generic textual element being updated/deleted by your own script using the DOM APIs. You could also make the scripts so optional for you to not need to provide a failure message, but that's not the right method when the scripts are needed for actually using the webpage.

And should be noted that WHATWG HTML contains a similar recommendation to the latter method:

The noscript element is a blunt instrument. Sometimes, scripts might be enabled, but for some reason the page's script might fail. For this reason, it's generally better to avoid using noscript, and to instead design the script to change the page from being a scriptless page to a scripted page on the fly, […]

Because the problem is, JavaScript can fail to load in several ways. Here's a non-exhaustive list of cases:

• Blocked domains/URLs, think adblockers/anti-viruses or corporate firewalls
• Blocked browsers/users, think hosting-side firewall (at any of the IP/TCP/HTTP/… level of encapsulation) which can be legitimate, over-zealous, or accidental
• Basic connectivity issues, after all browsing using mobile data is usual, HTTPS configurations still routinely presents expired certificates, BGP/DNS/… still fails
• Unsupported APIs or even language syntax, either due to a browser not supporting bleeding edge features or non-portable features
• Badly restored website backup or incomplete one
• Badly deployed website update, think HTML updated before JavaScript or even an incomplete deployment
• Part of the hosting infrastructure being down or overloaded
• Limits from the hoster, like rate-limits or limits on total bandwidth

I see most of the above on a regular basis, about multiple times per week to few times a month, and I tend to browse simple websites. And that's without counting the various ways scripts tend to fail at properly handling errors.