# safe-regex 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 WARNING: This module merely *seems* to work given all the catastrophic regular expressions I could find scouring the internet, but I don't have enough of a background in automata to be absolutely sure that this module will catch all exponential-time cases. [](https://ci.testling.com/substack/safe-regex) [](http://travis-ci.org/substack/safe-regex) # example ``` js var safe = require('safe-regex'); var 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 var safe = require('safe-regex') ``` ## var ok = safe(re, opts={}) Return a boolean `ok` whether or not the regex `re` is safe and not possibly catastrophic. `re` can be a `RegExp` object or just a string. If the `re` is a string and is an invalid regex, returns `false`. * `opts.limit` - maximum number of allowed repetitions in the entire regex. Default: `25`. # install With [npm](https://npmjs.org) do: ``` npm install safe-regex ``` # license MIT