README.md

# to-regex-range [![Donate](https://img.shields.io/badge/Donate-PayPal-green.svg)](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=W8YFZ425KND68) [![NPM version](https://img.shields.io/npm/v/to-regex-range.svg?style=flat)](https://www.npmjs.com/package/to-regex-range) [![NPM monthly downloads](https://img.shields.io/npm/dm/to-regex-range.svg?style=flat)](https://npmjs.org/package/to-regex-range) [![NPM total downloads](https://img.shields.io/npm/dt/to-regex-range.svg?style=flat)](https://npmjs.org/package/to-regex-range) [![Linux Build Status](https://img.shields.io/travis/micromatch/to-regex-range.svg?style=flat&label=Travis)](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
```

<details>
<summary><strong>What does this do?</strong></summary>

<br>

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).

<br>

</details>

<details>
<summary><strong>Why use this library?</strong></summary>

<br>

### 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

<br>

</details>

## 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

<details>
<summary><strong>Contributing</strong></summary>

Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).

</details>

<details>
<summary><strong>Running Tests</strong></summary>

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
```

</details>

<details>
<summary><strong>Building docs</strong></summary>

_(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
```

</details>

### 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)!

<a href="https://www.patreon.com/jonschlinkert">
<img src="https://c5.patreon.com/external/logo/become_a_patron_button@2x.png" height="50">
</a>

### 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._