RegExp.prototype.unicode examples are not helpful

[Marcono1234]

What information was incorrect, unhelpful, or incomplete?

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/unicode

The current example just shows how to access the property, it does not show at all what effect the Regex flag has.

What did you expect to see?

The example should show what difference the u flag has, at the very least something like:

const regex1 = new RegExp('\\u{61}');
const regex2 = new RegExp('\\u{61}', 'u');

console.log(regex1.unicode);
// Expected output: false

console.log(regex2.unicode);
// Expected output: true

console.log(regex1.test("a"));
// Expected output: false

console.log(regex2.test("a"));
// Expected output: true

However, the \\u{...} example might be a bit pointless because you can just write \u{...} which is understood uses a JavaScript escape sequence and therefore works regardless of whether the u flag is used or not (I assume).¹

A more interesting example might be to match a Unicode property, and / or to show that matching emojis (respectively in general any supplementary character) only works correctly when using the u flag.

Do you have any supporting links, references, or citations?

No response

Do you have anything more you want to share?

No response

Footnotes

1. This also highlights a bug with the current example; the \u{61} is (if I understand it correctly) a normal JavaScript escape, so the current example is equivalent to:

   const regex1 = new RegExp('a');
   const regex2 = new RegExp('a', 'u');
   

   ↩

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[Josh-Cena]

is understood uses a JavaScript escape sequence

\u{61} would be a string literal escape sequence; \\u{61} is the string literal form of /\u{61}/, which is actually a regex syntax of Unicode escape, which only works in u mode.

Ideally, we would have a separate page for the u flag (as part of mdn/content#22210), but I'm probably not going to do that in the end, so it makes sense to make the unicode example a bit more useful.