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# 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
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