zloirock/core-js

[RegExp] Match Indices

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#1,507 opened on Feb 5, 2026

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enhancementhelp wanted

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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

Research direction
Read the proposal at tc39/proposal regexp match indices and implement the 'd' flag support in core js's RegExp polyfill. The error shows that the 'd' flag is not recognized; you need to update the regexp constructor validation to accept 'd' and implement the matching indices behavior.
Tech stack
javascript
Domain
api
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaScriptRegExp
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60