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<details>
<summary><strong>What does this do?</strong></summary>
<br>
This libary generates the `source` string to be passed to `new RegExp()` for matching a range of numbers.
**Example**
```js
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).
<br>
</details>
<details>
<summary><strong>Why use this library?</strong></summary>
<br>
### 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](http://www.regular-expressions.info/charclass.html) and other regex features, I personally have always found [regular-expressions.info](http://www.regular-expressions.info/charclass.html) to be pretty useful.
### Heavily tested
As of {%= date() %}, this library runs [>1m test assertions](./test/test.js) 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
<br>
</details>
## Usage
Add this library to your javascript application with the following line of code
```js
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).
```js
const source = toRegexRange('15', '95');
//=> 1[5-9]|[2-8][0-9]|9[0-5]
const regex = new RegExp(`^${source}$`);
console.log(regex.test('14')); //=> false
console.log(regex.test('50')); //=> true
console.log(regex.test('94')); //=> true
console.log(regex.test('96')); //=> false
```
## Options
### options.capture
**Type**: `boolean`
**Deafault**: `undefined`
Wrap the returned value in parentheses when there is more than one regex condition. Useful when you're dynamically generating ranges.
```js
console.log(toRegexRange('-10', '10'));
//=> -[1-9]|-?10|[0-9]
console.log(toRegexRange('-10', '10', { capture: true }));
//=> (-[1-9]|-?10|[0-9])
```
### options.shorthand
**Type**: `boolean`
**Deafault**: `undefined`
Use the regex shorthand for `[0-9]`:
```js
console.log(toRegexRange('0', '999999'));
//=> [0-9]|[1-9][0-9]{1,5}
console.log(toRegexRange('0', '999999', { shorthand: true }));
//=> \d|[1-9]\d{1,5}
```
### options.relaxZeros
**Type**: `boolean`
**Default**: `true`
This option relaxes matching for leading zeros when when ranges are zero-padded.
```js
const source = toRegexRange('-0010', '0010');
const regex = new RegExp(`^${source}$`);
console.log(regex.test('-10')); //=> true
console.log(regex.test('-010')); //=> true
console.log(regex.test('-0010')); //=> true
console.log(regex.test('10')); //=> true
console.log(regex.test('010')); //=> true
console.log(regex.test('0010')); //=> true
```
When `relaxZeros` is false, matching is strict:
```js
const source = toRegexRange('-0010', '0010', { relaxZeros: false });
const regex = new RegExp(`^${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
{%= examples() %}
## Heads up!
**Order of arguments**
When the `min` is larger than the `max`, values will be flipped to create a valid range:
```js
toRegexRange('51', '29');
```
Is effectively flipped to:
```js
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
### v5.0.0 - 2019-04-07
Optimizations. Updated code to use newer ES features.
### 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](https://github.com/dimka665/range-regex).
|
