I didn't make myself clear. The embedded device is the web server in this setup. The browsing device (phone, tablet etc) runs javascript. You're right, no way a tiny embedded device runs javascript.
What if a device doesn't have a web browser? Or a display? Or a network connection? At some point you have to make some basic assumptions about the platform you're targeting.
There are many web browsers that don't support JavaScript, and JavaScript is something that can be quite easily turned off in many browsers that support it. Harder than it used to be, if anything.
Then there are those like myself that run NoScript or something similar where the author of the website has to entice me into allowing them to run javascript code on my computer. If I can find the correct one to enable out of the dozen or so that most websites seem to use.
At some point it,s time to give up. But before I do, I will bend over backwards twice to try to accomodate the user. Maybe it,s because of all those times some arrogant asshole website told me my browser isn,t goos enough.
My several years iPad with iOS 9, an otherwise capable device, locks up regularly on many js sites. JS is a global toggle which takes 30 seconds to switch.