You are missing the joke. The correct line would read:

  isHexadecimal("HADC0FFEE"); // false

I believe they're showing an example of where people would use (incorrect) regex patterns to validate. That's the whole thrust of the previous paragraph. `hadc0ffee` is not valid hex, but the function says it is due to, I presume, an incorrect regex pattern. I'm not familiar enough with regex to know why it's wrong though.

Edit: I was curious, so I looked through the linked docs for regex. They have the exact same pattern for checking hex in there as they do in this one. I guess it was just an error after all?

so, I thought there was some esoteric weirdness in the spec'd Javascript regex engine that made HADC0FFEE somehow match /^[0-9A-F]+$/i. Then the joke kinda makes sense right? I do need coffee to work with JS most of the time haha

But I do get false, running it in chrome dev tools.

When they're talking about writing documentation for tricky subjects, this misses a bit. I have no clue what the joke is, other than, if you haven't had coffee, you might think this evaluates to true?

I was also wondering what they were trying to say with that.

No issues here in Safari on iOS

Seeing the same on Android

no shaking here on firefox/android.

> It's funny Mozilla has a blog that renders about 20px to wide on mobile.

This is caused by the string "sha256-tG5mcZUtJsZvyKAxYLVXrmjKBVLd6VpVccqz/r4ypFE=" which does not wrap properly. Using "word-break: break-all;" on the pre element would fix it.

> The company that makes most of the web standards.

That is incorrect. Mozilla is only one of the several companies and working groups that may be involved. MDN is documentation, not specification.

Renders fine on Firefox Android (no horizontal scrolling), but I do see the extra width on Chromium based browsers

It doesn’t render at all on my ipad pro with iOS 13.7. Actually it does render and then immediately turns black. People give w3schools a lot of flak but at least it renders and is usable on my ipad unlike the MDN docs. Do we no longer care about backwards compatibility, it seems not and that’s shameful.