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Pass two numbers, get a regex-compatible source string for matching ranges. Validated against more than 2.87 million test assertions.

Package Exports

  • to-regex-range

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (to-regex-range) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

to-regex-range NPM version NPM monthly downloads NPM total downloads Linux Build Status

Pass two numbers, get a regex-compatible source string for matching ranges. Validated against more than 2.87 million test assertions.

Install

Install with npm:

$ npm install --save to-regex-range

Install with yarn:

$ yarn add 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

var toRegexRange = require('to-regex-range');
var 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 22, 2017, this library runs 2,783,483 test assertions against generated regex-ranges to provide brute-force verification that results are indeed correct.

Tests run in ~870ms on my MacBook Pro, 2.5 GHz Intel Core i7.

Highly optimized

Generated regular expressions are highly 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

var 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).

var source = toRegexRange('15', '95');
//=> 1[5-9]|[2-8][0-9]|9[0-5]

var re = new RegExp('^' + source + '$');
console.log(re.test('14')); //=> false
console.log(re.test('50')); //=> true
console.log(re.test('94')); //=> true
console.log(re.test('96')); //=> false

Examples

Range Result Compile time
toRegexRange('5, 5') 5 26μs
toRegexRange('5, 6') 5|6 47μs
toRegexRange('29, 51') 29|[3-4][0-9]|5[0-1] 452μs
toRegexRange('31, 877') 3[1-9]|[4-9][0-9]|[1-7][0-9]{2}|8[0-6][0-9]|87[0-7] 756μs
toRegexRange('111, 555') 11[1-9]|1[2-9][0-9]|[2-4][0-9]{2}|5[0-4][0-9]|55[0-5] 61μs
toRegexRange('-10, 10') -[1-9]|-?10|[0-9] 69μs
toRegexRange('-100, -10') -1[0-9]|-[2-9][0-9]|-100 42μs
toRegexRange('-100, 100') -[1-9]|-?[1-9][0-9]|-?100|[0-9] 42μs
toRegexRange('001, 100') 0{2}[1-9]|0[1-9][0-9]|100 135μs
toRegexRange('0010, 1000') 0{2}1[0-9]|0{2}[2-9][0-9]|0[1-9][0-9]{2}|1000 53μs
toRegexRange('1, 2') 1|2 18μs
toRegexRange('1, 5') [1-5] 23μs
toRegexRange('1, 10') [1-9]|10 22μs
toRegexRange('1, 100') [1-9]|[1-9][0-9]|100 23μs
toRegexRange('1, 1000') [1-9]|[1-9][0-9]{1,2}|1000 60μs
toRegexRange('1, 10000') [1-9]|[1-9][0-9]{1,3}|10000 117μs
toRegexRange('1, 100000') [1-9]|[1-9][0-9]{1,4}|100000 42μs
toRegexRange('1, 1000000') [1-9]|[1-9][0-9]{1,5}|1000000 46μs
toRegexRange('1, 10000000') [1-9]|[1-9][0-9]{1,6}|10000000 60μs

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

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

Contributing

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

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

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

Author

Jon Schlinkert

License

Copyright © 2017, Jon Schlinkert. Released under the MIT License.

This file was generated by verb-generate-readme, v0.5.0, on April 22, 2017.