zloirock/core-js

[RegExp] Match Indices

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#1507 opened on Feb 5, 2026

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 (2 comments) (0 reactions) (0 assignees)JavaScript (23,771 stars) (1,609 forks)batch import
enhancementhelp wanted

Description

execute: const test = new RegExp('.', 'd'); output: Uncaught SyntaxError: Invalid flags supplied to RegExp constructor 'd' at new RegExp () at :1:14 (anonymous) @ VM524:1

https://github.com/tc39/proposal-regexp-match-indices

Contributor guide

Tech stack
javascript
Domain
api
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic JavaScriptRegExp flag handlingcore js build process
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80
Research direction
Research the RegExp match indices proposal at the linked TC39 proposal. In core js, locate the RegExp constructor implementation where flags are validated, and add support for the 'd' flag. Update the list of allowed flags in the constructor and ensure the 'd' flag is recognized. Add corresponding tests following existing patterns.