to-regex-range

What is to-regex-range?

The to-regex-range npm package is designed to generate regular expressions for matching numeric ranges. It is useful for creating regex patterns that can match against specific ranges of numbers, allowing for precise control over numeric input validation, among other applications.

What are to-regex-range's main functionalities?

Generating regex for simple numeric ranges

This feature allows you to generate a regex pattern for a simple numeric range, such as from 5 to 10. The resulting regex will match any number within this range.

const toRegexRange = require('to-regex-range');
const regex = toRegexRange('5', '10');
console.log(regex); // => '5|6|7|8|9|10'

Creating regex with zero-padding

This feature enables the generation of regex patterns that account for zero-padded numbers, useful for matching numbers within a range where the number of digits is consistent.

const toRegexRange = require('to-regex-range');
const regex = toRegexRange('001', '100', { capture: true, pad: true });
console.log(regex); // Example output: '(0[0-9]{2}|1[0-9]{2})'

Generating regex for complex ranges with options

This feature allows for the creation of regex patterns for more complex numeric ranges with additional options, such as disabling the relaxation of leading zeros, providing more precise control over the matching behavior.

const toRegexRange = require('to-regex-range');
const regex = toRegexRange('10', '299', { relaxZeros: false });
console.log(regex); // Example output: '1[0-9]|2[0-9]{2}'

0

README

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 :heart: 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

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 July 04, 2018, 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

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 only applies to negative zero-padded ranges. By default, when a negative zero-padded range is defined, the number of leading zeros is relaxed using -0*.

console.log(toRegexRange('-001', '100'));
//=> -0*1|0{2}[0-9]|0[1-9][0-9]|100

console.log(toRegexRange('-001', '100', {relaxZeros: false}));
//=> -0{2}1|0{2}[0-9]|0[1-9][0-9]|100

Why are zeros relaxed for negative zero-padded ranges by default?

Consider the following.

var regex = toRegexRange('-001', '100');

Note that -001 and 100 are both three digits long.

In most zero-padding implementations, only a single leading zero is enough to indicate that zero-padding should be applied. Thus, the leading zeros would be "corrected" on the negative range in the example to -01, instead of -001, to make total length of each string no greater than the length of the largest number in the range (in other words, -001 is 4 digits, but 100 is only three digits).

If zeros were not relaxed by default, you might expect the resulting regex of the above pattern to match -001 - given that it's defined that way in the arguments - but it wouldn't. It would, however, match -01. This gets even more ambiguous with large ranges, like -01 to 1000000.

Thus, we relax zeros by default to provide a more predictable experience for users.

Examples

Range	Result	Compile time
toRegexRange('5, 5')	5	15μs
toRegexRange('5, 6')	`5\	6`
toRegexRange('29, 51')	`29\	34\
toRegexRange('31, 877')	`3[1-9]\	4-9\
toRegexRange('111, 555')	`11[1-9]\	12-9\
toRegexRange('-10, 10')	`-[1-9]\	-?10\
toRegexRange('-100, -10')	`-10-9\	-2-9\
toRegexRange('-100, 100')	`-[1-9]\	-?1-9\
toRegexRange('001, 100')	`0{2}[1-9]\	01-9\
toRegexRange('0010, 1000')	`0{2}10-9\	0{2}2-9\
toRegexRange('1, 2')	`1\	2`
toRegexRange('1, 5')	[1-5]	26μs
toRegexRange('1, 10')	`[1-9]\	10`
toRegexRange('1, 100')	`[1-9]\	1-9\
toRegexRange('1, 1000')	`[1-9]\	1-9\
toRegexRange('1, 10000')	`[1-9]\	1-9\
toRegexRange('1, 100000')	`[1-9]\	1-9\
toRegexRange('1, 1000000')	`[1-9]\	1-9\
toRegexRange('1, 10000000')	`[1-9]\	1-9\

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
56	jonschlinkert
2	realityking

Author

Jon Schlinkert

• LinkedIn Profile
• GitHub Profile
• Twitter Profile

License

Copyright © 2018, Jon Schlinkert. Released under the MIT License.

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This file was generated by verb-generate-readme, v0.6.0, on July 04, 2018.