zloirock/core-js

[RegExp] Match Indices

Open

#1,507 opened on Feb 5, 2026

View on GitHubContributor guide
 (2 comments) (0 reactions) (0 assignees)JavaScript (1,609 forks)batch import
enhancementhelp wanted

Repository metrics

Stars
 (23,771 stars)
PR merge metrics
 (No merged PRs in 30d)

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