# safe-regex2 [](https://github.com/fastify/safe-regex2/actions/workflows/ci.yml) [](https://www.npmjs.com/package/safe-regex2) [](https://github.com/neostandard/neostandard) Detect potentially [catastrophic](http://regular-expressions.mobi/catastrophic.html) [exponential-time](http://perlgeek.de/blog-en/perl-tips/in-search-of-an-exponetial-regexp.html) regular expressions by limiting the [star height](https://en.wikipedia.org/wiki/Star_height) to 1. This is a fork of https://github.com/substack/safe-regex at 1.1.0. WARNING: This module has both false positives and false negatives. It is not meant as a full checker, but it detects basic cases. ## Install ``` npm i safe-regex2 ``` ## Example ``` js const safe = require('safe-regex2'); const regex = process.argv.slice(2).join(' '); console.log(safe(regex)); ``` ``` $ node safe.js '(x+x+)+y' false $ node safe.js '(beep|boop)*' true $ node safe.js '(a+){10}' false $ node safe.js '\blocation\s*:[^:\n]+\b(Oakland|San Francisco)\b' true ``` ## Methods ``` js const safe = require('safe-regex') ``` ### const ok = safe(re, opts={}) Returns a boolean indicating whether the regex `re` is safe and not possibly catastrophic. `re` can be a `RegExp` object or just a string. If `re` is a string and is an invalid regex, it returns `false`. * `opts.limit` - maximum number of allowed repetitions in the entire regex. Default: `25`. ## License Licensed under [MIT](./LICENSE).