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, and consider starring the project to show your ❤️ and support.

Install

Install with npm:

$ 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

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 and other regex features, I personally have always found regular-expressions.info to be pretty useful.

Heavily tested

As of April 07, 2019, this library runs >1m test assertions 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

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).

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.

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]:

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.

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:

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:

toRegexRange('51', '29');

Is effectively flipped to:

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.

About

Contributing

Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.

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:

$ npm install && npm test

Building docs

(This project's readme.md is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the .verb.md readme template.)

To generate the readme, run the following command:

$ npm install -g verbose/verb#dev verb-generate-readme && verb

Related projects

You might also be interested in these projects:

• expand-range: Fast, bash-like range expansion. Expand a range of numbers or letters, uppercase or lowercase. Used… more | homepage

• fill-range: Fill in a range of numbers or letters, optionally passing an increment or step to… more | homepage

• micromatch: Glob matching for javascript/node.js. A drop-in replacement and faster alternative to minimatch and multimatch. | homepage

• repeat-element: Create an array by repeating the given value n times. | homepage

• repeat-string: Repeat the given string n times. Fastest implementation for repeating a string. | homepage

Contributors

Commits	Contributor
63	jonschlinkert
3	doowb
2	realityking

Author

Jon Schlinkert

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Please consider supporting me on Patreon, or start your own Patreon page!

License

Copyright © 2019, Jon Schlinkert. Released under the MIT License.

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This file was generated by verb-generate-readme, v0.8.0, on April 07, 2019.