Misleading "try it" example for RegExp unicode flag

[pewscorner]

MDN URL

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

What specific section or headline is this issue about?

The "try it" example.

What information was incorrect, unhelpful, or incomplete?

The example uses new RegExp('\u{61}', 'u') with and without the 'u' flag to demonstrate the difference. But '\u{61}' immediately gets converted to 'a' (and becomes the value of the RegExp source property) as part of normal string literal interpretation before the string is passed to RegExp, so the 'u' flag has no effect.

What did you expect to see?

To introduce an effect, the example would need to be rewritten to use one of the following syntaxes:

1. new RegExp('\\u{61}', 'u') (note: 2 backslashes instead of 1)
2. /\u{61}/u

Furthermore, to make the effect of the flag clear, it is not enough to show the value of the source property. The result of a match needs to be shown, e.g.:

console.log(regex1.exec('a'));
// Expected output: null
console.log(regex1.exec('u'.repeat(61)));
// Expected output: Array ["uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu"]

console.log(regex2.exec('a'));
// Expected output: Array ["a"]
console.log(regex2.exec('u'.repeat(61)));
// Expected output: null

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

No response

Do you have anything more you want to share?

No response

MDN metadata

Page report details

• Folder: en-us/web/javascript/reference/global_objects/regexp/unicode
• MDN URL: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/unicode
• GitHub URL: https://github.com/mdn/content/blob/main/files/en-us/web/javascript/reference/global_objects/regexp/unicode/index.md
• Last commit: c2445ce
• Document last modified: 2023-09-12T02:17:31.000Z

[Josh-Cena]

Duplicate of mdn/interactive-examples#2490