to-regex-range

Pass two numbers, get a regex-compatible source string for matching ranges. Validated against more than 2.78 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 27, 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

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	33μs
toRegexRange('5, 6')	5|6	53μs
toRegexRange('29, 51')	29|[34][0-9]|5[01]	699μs
toRegexRange('31, 877')	3[1-9]|[4-9][0-9]|[1-7][0-9]{2}|8[0-6][0-9]|87[0-7]	711μs
toRegexRange('111, 555')	11[1-9]|1[2-9][0-9]|[2-4][0-9]{2}|5[0-4][0-9]|55[0-5]	62μs
toRegexRange('-10, 10')	-[1-9]|-?10|[0-9]	74μs
toRegexRange('-100, -10')	-1[0-9]|-[2-9][0-9]|-100	49μs
toRegexRange('-100, 100')	-[1-9]|-?[1-9][0-9]|-?100|[0-9]	45μs
toRegexRange('001, 100')	0{2}[1-9]|0[1-9][0-9]|100	158μs
toRegexRange('0010, 1000')	0{2}1[0-9]|0{2}[2-9][0-9]|0[1-9][0-9]{2}|1000	61μs
toRegexRange('1, 2')	1|2	10μs
toRegexRange('1, 5')	[1-5]	24μs
toRegexRange('1, 10')	[1-9]|10	23μs
toRegexRange('1, 100')	[1-9]|[1-9][0-9]|100	30μs
toRegexRange('1, 1000')	[1-9]|[1-9][0-9]{1,2}|1000	52μs
toRegexRange('1, 10000')	[1-9]|[1-9][0-9]{1,3}|10000	47μs
toRegexRange('1, 100000')	[1-9]|[1-9][0-9]{1,4}|100000	44μs
toRegexRange('1, 1000000')	[1-9]|[1-9][0-9]{1,5}|1000000	49μs
toRegexRange('1, 10000000')	[1-9]|[1-9][0-9]{1,6}|10000000	63μs

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

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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

• github/jonschlinkert

• twitter/jonschlinkert

License

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

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This file was generated by verb-generate-readme, v0.6.0, on April 27, 2017.