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('{%= name %}');
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?
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
1through5=>/[1-5]/(not bad...) - regex for matching
1or5=>/(1|5)/(still easy...) - regex for matching
1through50=>/([1-9]|[1-4][0-9]|50)/(uh-oh...) - regex for matching
1through55=>/([1-9]|[1-4][0-9]|5[0-5])/(no prob, I can do this...) - regex for matching
1through555=>/([1-9]|[1-9][0-9]|[1-4][0-9]{2}|5[0-4][0-9]|55[0-5])/(maybe not...) - regex for matching
0001through5555=>/(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.
As of {%= date() %}, 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.
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
Add this library to your javascript application with the following line of code
const toRegexRange = require('{%= name %}');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')); //=> falseType: 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])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}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')); //=> trueWhen 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() %}
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.
Optimizations. Updated code to use newer ES features.
New features
Adds support for zero-padding!
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.
Inspired by the python library range-regex.