# to-regex-range [](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=W8YFZ425KND68) [](https://www.npmjs.com/package/to-regex-range) [](https://npmjs.org/package/to-regex-range) [](https://npmjs.org/package/to-regex-range) [](https://travis-ci.org/micromatch/to-regex-range)
> Pass two numbers, get a regex-compatible source string for matching ranges. Validated against more than 2.78 million test assertions.
Please consider following this project's author, [Jon Schlinkert](https://github.com/jonschlinkert), and consider starring the project to show your :heart: and support.
## Install
Install with [npm](https://www.npmjs.com/):
```sh
$ npm install --save to-regex-range
```
What does this do?
This libary generates the `source` string to be passed to `new RegExp()` for matching a range of numbers.
**Example**
```js
const toRegexRange = require('to-regex-range');
const regex = new RegExp(toRegexRange('15', '95'));
```
A string is returned so that you can do whatever you need with it before passing it to `new RegExp()` (like adding `^` or `$` boundaries, defining flags, or combining it another string).
Why use this library?
### Convenience
Creating regular expressions for matching numbers gets deceptively complicated pretty fast.
For example, let's say you need a validation regex for matching part of a user-id, postal code, social security number, tax id, etc:
* regex for matching `1` => `/1/` (easy enough)
* regex for matching `1` through `5` => `/[1-5]/` (not bad...)
* regex for matching `1` or `5` => `/(1|5)/` (still easy...)
* regex for matching `1` through `50` => `/([1-9]|[1-4][0-9]|50)/` (uh-oh...)
* regex for matching `1` through `55` => `/([1-9]|[1-4][0-9]|5[0-5])/` (no prob, I can do this...)
* regex for matching `1` through `555` => `/([1-9]|[1-9][0-9]|[1-4][0-9]{2}|5[0-4][0-9]|55[0-5])/` (maybe not...)
* regex for matching `0001` through `5555` => `/(0{3}[1-9]|0{2}[1-9][0-9]|0[1-9][0-9]{2}|[1-4][0-9]{3}|5[0-4][0-9]{2}|55[0-4][0-9]|555[0-5])/` (okay, I get the point!)
The numbers are contrived, but they're also really basic. In the real world you might need to generate a regex on-the-fly for validation.
**Learn more**
If you're interested in learning more about [character classes](http://www.regular-expressions.info/charclass.html) and other regex features, I personally have always found [regular-expressions.info](http://www.regular-expressions.info/charclass.html) to be pretty useful.
### Heavily tested
As of April 07, 2019, this library runs [>1m test assertions](./test/test.js) against generated regex-ranges to provide brute-force verification that results are correct.
Tests run in ~280ms on my MacBook Pro, 2.5 GHz Intel Core i7.
### Optimized
Generated regular expressions are optimized:
* duplicate sequences and character classes are reduced using quantifiers
* smart enough to use `?` conditionals when number(s) or range(s) can be positive or negative
* uses fragment caching to avoid processing the same exact string more than once
## Usage
Add this library to your javascript application with the following line of code
```js
const toRegexRange = require('to-regex-range');
```
The main export is a function that takes two integers: the `min` value and `max` value (formatted as strings or numbers).
```js
const source = toRegexRange('15', '95');
//=> 1[5-9]|[2-8][0-9]|9[0-5]
const regex = new RegExp(`^${source}$`);
console.log(regex.test('14')); //=> false
console.log(regex.test('50')); //=> true
console.log(regex.test('94')); //=> true
console.log(regex.test('96')); //=> false
```
## Options
### options.capture
**Type**: `boolean`
**Deafault**: `undefined`
Wrap the returned value in parentheses when there is more than one regex condition. Useful when you're dynamically generating ranges.
```js
console.log(toRegexRange('-10', '10'));
//=> -[1-9]|-?10|[0-9]
console.log(toRegexRange('-10', '10', { capture: true }));
//=> (-[1-9]|-?10|[0-9])
```
### options.shorthand
**Type**: `boolean`
**Deafault**: `undefined`
Use the regex shorthand for `[0-9]`:
```js
console.log(toRegexRange('0', '999999'));
//=> [0-9]|[1-9][0-9]{1,5}
console.log(toRegexRange('0', '999999', { shorthand: true }));
//=> \d|[1-9]\d{1,5}
```
### options.relaxZeros
**Type**: `boolean`
**Default**: `true`
This option relaxes matching for leading zeros when when ranges are zero-padded.
```js
const source = toRegexRange('-0010', '0010');
const regex = new RegExp(`^${source}$`);
console.log(regex.test('-10')); //=> true
console.log(regex.test('-010')); //=> true
console.log(regex.test('-0010')); //=> true
console.log(regex.test('10')); //=> true
console.log(regex.test('010')); //=> true
console.log(regex.test('0010')); //=> true
```
When `relaxZeros` is false, matching is strict:
```js
const source = toRegexRange('-0010', '0010', { relaxZeros: false });
const regex = new RegExp(`^${source}$`);
console.log(regex.test('-10')); //=> false
console.log(regex.test('-010')); //=> false
console.log(regex.test('-0010')); //=> true
console.log(regex.test('10')); //=> false
console.log(regex.test('010')); //=> false
console.log(regex.test('0010')); //=> true
```
## Examples
| **Range** | **Result** | **Compile time** |
| --- | --- | --- |
| `toRegexRange(-10, 10)` | `-[1-9]\|-?10\|[0-9]` | _132μs_ |
| `toRegexRange(-100, -10)` | `-1[0-9]\|-[2-9][0-9]\|-100` | _50μs_ |
| `toRegexRange(-100, 100)` | `-[1-9]\|-?[1-9][0-9]\|-?100\|[0-9]` | _42μs_ |
| `toRegexRange(001, 100)` | `0{0,2}[1-9]\|0?[1-9][0-9]\|100` | _109μs_ |
| `toRegexRange(001, 555)` | `0{0,2}[1-9]\|0?[1-9][0-9]\|[1-4][0-9]{2}\|5[0-4][0-9]\|55[0-5]` | _51μs_ |
| `toRegexRange(0010, 1000)` | `0{0,2}1[0-9]\|0{0,2}[2-9][0-9]\|0?[1-9][0-9]{2}\|1000` | _31μs_ |
| `toRegexRange(1, 50)` | `[1-9]\|[1-4][0-9]\|50` | _24μs_ |
| `toRegexRange(1, 55)` | `[1-9]\|[1-4][0-9]\|5[0-5]` | _23μs_ |
| `toRegexRange(1, 555)` | `[1-9]\|[1-9][0-9]\|[1-4][0-9]{2}\|5[0-4][0-9]\|55[0-5]` | _30μs_ |
| `toRegexRange(1, 5555)` | `[1-9]\|[1-9][0-9]{1,2}\|[1-4][0-9]{3}\|5[0-4][0-9]{2}\|55[0-4][0-9]\|555[0-5]` | _43μs_ |
| `toRegexRange(111, 555)` | `11[1-9]\|1[2-9][0-9]\|[2-4][0-9]{2}\|5[0-4][0-9]\|55[0-5]` | _38μs_ |
| `toRegexRange(29, 51)` | `29\|[34][0-9]\|5[01]` | _24μs_ |
| `toRegexRange(31, 877)` | `3[1-9]\|[4-9][0-9]\|[1-7][0-9]{2}\|8[0-6][0-9]\|87[0-7]` | _32μs_ |
| `toRegexRange(5, 5)` | `5` | _8μs_ |
| `toRegexRange(5, 6)` | `5\|6` | _11μs_ |
| `toRegexRange(1, 2)` | `1\|2` | _6μs_ |
| `toRegexRange(1, 5)` | `[1-5]` | _15μs_ |
| `toRegexRange(1, 10)` | `[1-9]\|10` | _22μs_ |
| `toRegexRange(1, 100)` | `[1-9]\|[1-9][0-9]\|100` | _25μs_ |
| `toRegexRange(1, 1000)` | `[1-9]\|[1-9][0-9]{1,2}\|1000` | _31μs_ |
| `toRegexRange(1, 10000)` | `[1-9]\|[1-9][0-9]{1,3}\|10000` | _34μs_ |
| `toRegexRange(1, 100000)` | `[1-9]\|[1-9][0-9]{1,4}\|100000` | _36μs_ |
| `toRegexRange(1, 1000000)` | `[1-9]\|[1-9][0-9]{1,5}\|1000000` | _42μs_ |
| `toRegexRange(1, 10000000)` | `[1-9]\|[1-9][0-9]{1,6}\|10000000` | _42μs_ |
## Heads up!
**Order of arguments**
When the `min` is larger than the `max`, values will be flipped to create a valid range:
```js
toRegexRange('51', '29');
```
Is effectively flipped to:
```js
toRegexRange('29', '51');
//=> 29|[3-4][0-9]|5[0-1]
```
**Steps / increments**
This library does not support steps (increments). A pr to add support would be welcome.
## History
### v2.0.0 - 2017-04-21
**New features**
Adds support for zero-padding!
### v1.0.0
**Optimizations**
Repeating ranges are now grouped using quantifiers. rocessing time is roughly the same, but the generated regex is much smaller, which should result in faster matching.
## Attribution
Inspired by the python library [range-regex](https://github.com/dimka665/range-regex).
## About
Contributing
Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
Running Tests
Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:
```sh
$ npm install && npm test
```
Building docs
_(This project's readme.md is generated by [verb](https://github.com/verbose/verb-generate-readme), please don't edit the readme directly. Any changes to the readme must be made in the [.verb.md](.verb.md) readme template.)_
To generate the readme, run the following command:
```sh
$ npm install -g verbose/verb#dev verb-generate-readme && verb
```
### Related projects
You might also be interested in these projects:
* [expand-range](https://www.npmjs.com/package/expand-range): Fast, bash-like range expansion. Expand a range of numbers or letters, uppercase or lowercase. Used… [more](https://github.com/jonschlinkert/expand-range) | [homepage](https://github.com/jonschlinkert/expand-range "Fast, bash-like range expansion. Expand a range of numbers or letters, uppercase or lowercase. Used by micromatch.")
* [fill-range](https://www.npmjs.com/package/fill-range): Fill in a range of numbers or letters, optionally passing an increment or `step` to… [more](https://github.com/jonschlinkert/fill-range) | [homepage](https://github.com/jonschlinkert/fill-range "Fill in a range of numbers or letters, optionally passing an increment or `step` to use, or create a regex-compatible range with `options.toRegex`")
* [micromatch](https://www.npmjs.com/package/micromatch): Glob matching for javascript/node.js. A drop-in replacement and faster alternative to minimatch and multimatch. | [homepage](https://github.com/micromatch/micromatch "Glob matching for javascript/node.js. A drop-in replacement and faster alternative to minimatch and multimatch.")
* [repeat-element](https://www.npmjs.com/package/repeat-element): Create an array by repeating the given value n times. | [homepage](https://github.com/jonschlinkert/repeat-element "Create an array by repeating the given value n times.")
* [repeat-string](https://www.npmjs.com/package/repeat-string): Repeat the given string n times. Fastest implementation for repeating a string. | [homepage](https://github.com/jonschlinkert/repeat-string "Repeat the given string n times. Fastest implementation for repeating a string.")
### Contributors
| **Commits** | **Contributor** |
| --- | --- |
| 63 | [jonschlinkert](https://github.com/jonschlinkert) |
| 3 | [doowb](https://github.com/doowb) |
| 2 | [realityking](https://github.com/realityking) |
### Author
**Jon Schlinkert**
* [GitHub Profile](https://github.com/jonschlinkert)
* [Twitter Profile](https://twitter.com/jonschlinkert)
* [LinkedIn Profile](https://linkedin.com/in/jonschlinkert)
Please consider supporting me on Patreon, or [start your own Patreon page](https://patreon.com/invite/bxpbvm)!
### License
Copyright © 2019, [Jon Schlinkert](https://github.com/jonschlinkert).
Released under the [MIT License](LICENSE).
***
_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.8.0, on April 07, 2019._