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# safe-regex
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detect potentially
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[catastrophic](http://regular-expressions.mobi/catastrophic.html)
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[exponential-time](http://perlgeek.de/blog-en/perl-tips/in-search-of-an-exponetial-regexp.html)
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regular expressions by limiting the
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[star height](https://en.wikipedia.org/wiki/Star_height) to 1
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WARNING: This module merely *seems* to work given all the catastrophic regular
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expressions I could find scouring the internet, but I don't have enough of a
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background in automata to be absolutely sure that this module will catch all
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exponential-time cases.
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[](https://ci.testling.com/substack/safe-regex)
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[](http://travis-ci.org/substack/safe-regex)
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# example
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``` js
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var safe = require('safe-regex');
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var regex = process.argv.slice(2).join(' ');
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console.log(safe(regex));
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```
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```
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$ node safe.js '(x+x+)+y'
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false
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$ node safe.js '(beep|boop)*'
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true
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$ node safe.js '(a+){10}'
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false
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$ node safe.js '\blocation\s*:[^:\n]+\b(Oakland|San Francisco)\b'
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true
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```
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# methods
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``` js
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var safe = require('safe-regex')
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```
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## var ok = safe(re, opts={})
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Return a boolean `ok` whether or not the regex `re` is safe and not possibly
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catastrophic.
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`re` can be a `RegExp` object or just a string.
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If the `re` is a string and is an invalid regex, returns `false`.
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* `opts.limit` - maximum number of allowed repetitions in the entire regex.
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Default: `25`.
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# install
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With [npm](https://npmjs.org) do:
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```
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npm install safe-regex
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```
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# license
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MIT
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