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no-useless-escape false negative

See original GitHub issue

Tell us about your environment

ESLint Version: 3.12.2
Node Version: 7.2.1
npm Version: 3.10.10

What parser (default, Babel-ESLint, etc.) are you using?

default

Please show your full configuration: n/a, no configuration file

What did you do? Please include the actual source code causing the issue.

Running eslint --no-eslintrc --rule 'no-useless-escape: 2' test.js with the contents of `test.js being:

/\{/

Also same results with this more complete example:

console.log(/\{/.test('{')); // true

console.log(/{/.test('{')); // also true

What did you expect to happen?

I expected to be told that { was being uselessly escaped on line 1.

What actually happened? Please include the actual, raw output from ESLint.

No error reported. This issue also applies to /\}/.

Issue Analytics

State:
Created 7 years ago
Comments:5 (5 by maintainers)

Top GitHub Comments

2reactions

not-an-aardvarkcommented, Dec 19, 2016

Actually, after looking at the spec I’m not sure this is a bug – see this comment for more explanation. /{/ is only a legal regex for engines that implement Annex B, a part of the spec which is only normative for engines in web browsers. So /\{/ is only a useless escape on engines that implement Annex B, which might not apply to all engines.

1reaction

not-an-aardvarkcommented, Dec 24, 2016

Closing this issue – as described above, /\{/ is only a useless escape for engines that implement Annex B, but it’s not useless for JS engines in general.