1 # regex-cache [![NPM version](https://img.shields.io/npm/v/regex-cache.svg?style=flat)](https://www.npmjs.com/package/regex-cache) [![NPM downloads](https://img.shields.io/npm/dm/regex-cache.svg?style=flat)](https://npmjs.org/package/regex-cache) [![Build Status](https://img.shields.io/travis/jonschlinkert/regex-cache.svg?style=flat)](https://travis-ci.org/jonschlinkert/regex-cache)
3 > Memoize the results of a call to the RegExp constructor, avoiding repetitious runtime compilation of the same string and options, resulting in suprising performance improvements.
7 Install with [npm](https://www.npmjs.com/):
10 $ npm install regex-cache --save
13 * Read [what this does](#what-this-does).
14 * See [the benchmarks](#benchmarks)
18 Wrap a function like this:
21 var cache = require('regex-cache');
22 var someRegex = cache(require('some-regex-lib'));
27 If you want to cache a regex after calling `new RegExp()`, or you're requiring a module that returns a regex, wrap it with a function first:
30 var cache = require('regex-cache');
32 function yourRegex(str, opts) {
33 // do stuff to str and opts
34 return new RegExp(str, opts.flags);
37 var regex = cache(yourRegex);
44 * **No options are passed** to the function that creates the regex. Regardless of how big or small the regex is, when zero options are passed, caching will be faster than not.
45 * **A few options are passed**, and the values are primitives. The limited benchmarks I did show that caching is beneficial when up to 8 or 9 options are passed.
47 ### Do not use this when...
49 * **The values of options are not primitives**. When non-primitives must be compared for equality, the time to compare the options is most likely as long or longer than the time to just create a new regex.
51 ### Example benchmarks
53 Performance results, with and without regex-cache:
56 # no args passed (defaults)
57 with-cache x 8,699,231 ops/sec ±0.86% (93 runs sampled)
58 without-cache x 2,777,551 ops/sec ±0.63% (95 runs sampled)
60 # string and six options passed
61 with-cache x 1,885,934 ops/sec ±0.80% (93 runs sampled)
62 without-cache x 1,256,893 ops/sec ±0.65% (97 runs sampled)
65 with-cache x 7,723,256 ops/sec ±0.87% (92 runs sampled)
66 without-cache x 2,303,060 ops/sec ±0.47% (99 runs sampled)
69 with-cache x 4,179,877 ops/sec ±0.53% (100 runs sampled)
70 without-cache x 2,198,422 ops/sec ±0.47% (95 runs sampled)
73 with-cache x 3,256,222 ops/sec ±0.51% (99 runs sampled)
74 without-cache x 2,121,401 ops/sec ±0.79% (97 runs sampled)
77 with-cache x 1,816,018 ops/sec ±1.08% (96 runs sampled)
78 without-cache x 1,157,176 ops/sec ±0.53% (100 runs sampled)
81 # diminishing returns happen about here
85 with-cache x 1,210,598 ops/sec ±0.56% (92 runs sampled)
86 without-cache x 1,665,588 ops/sec ±1.07% (100 runs sampled)
88 # twelve options passed
89 with-cache x 1,042,096 ops/sec ±0.68% (92 runs sampled)
90 without-cache x 1,389,414 ops/sec ±0.68% (97 runs sampled)
92 # twenty options passed
93 with-cache x 661,125 ops/sec ±0.80% (93 runs sampled)
94 without-cache x 1,208,757 ops/sec ±0.65% (97 runs sampled)
97 # when non-primitive values are compared
100 # single value on the options is an object
101 with-cache x 1,398,313 ops/sec ±1.05% (95 runs sampled)
102 without-cache x 2,228,281 ops/sec ±0.56% (99 runs sampled)
107 Install dev dependencies:
110 npm i -d && npm run benchmarks
115 If you're using `new RegExp('foo')` instead of a regex literal, it's probably because you need to dyamically generate a regex based on user options or some other potentially changing factors.
117 When your function creates a string based on user inputs and passes it to the `RegExp` constructor, regex-cache caches the results. The next time the function is called if the key of a cached regex matches the user input (or no input was given), the cached regex is returned, avoiding unnecessary runtime compilation.
119 Using the RegExp constructor offers a lot of flexibility, but the runtime compilation comes at a price - it's slow. Not specifically because of the call to the RegExp constructor, but **because you have to build up the string before `new RegExp()` is even called**.
122 Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](https://github.com/jonschlinkert/regex-cache/issues/new).
126 Generate readme and API documentation with [verb](https://github.com/verbose/verb):
129 $ npm install verb && npm run docs
132 Or, if [verb](https://github.com/verbose/verb) is installed globally:
140 Install dev dependencies:
143 $ npm install -d && npm test
150 * [github/jonschlinkert](https://github.com/jonschlinkert)
151 * [twitter/jonschlinkert](http://twitter.com/jonschlinkert)
155 Copyright © 2016, [Jon Schlinkert](https://github.com/jonschlinkert).
156 Released under the [MIT license](https://github.com/jonschlinkert/regex-cache/blob/master/LICENSE).
160 _This file was generated by [verb](https://github.com/verbose/verb), v, on April 01, 2016._