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https://github.com/fent/randexp.js
Create random strings that match a given regular expression.
https://github.com/fent/randexp.js
node regular-expression testing
Last synced: about 2 months ago
JSON representation
Create random strings that match a given regular expression.
- Host: GitHub
- URL: https://github.com/fent/randexp.js
- Owner: fent
- License: mit
- Created: 2011-12-06T14:34:17.000Z (almost 13 years ago)
- Default Branch: master
- Last Pushed: 2024-01-17T22:27:51.000Z (8 months ago)
- Last Synced: 2024-05-28T07:08:23.715Z (4 months ago)
- Topics: node, regular-expression, testing
- Language: JavaScript
- Homepage: http://fent.github.io/randexp.js/
- Size: 607 KB
- Stars: 1,806
- Watchers: 32
- Forks: 91
- Open Issues: 12
-
Metadata Files:
- Readme: README.md
- Funding: .github/FUNDING.yml
- License: LICENSE
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README
# randexp.js
randexp will generate a random string that matches a given RegExp Javascript object.
[](https://david-dm.org/fent/randexp.js)
[](https://codecov.io/gh/fent/randexp.js)
# Usage
```js
const RandExp = require('randexp');
// supports grouping and piping
new RandExp(/hello+ (world|to you)/).gen();
// => hellooooooooooooooooooo world
// sets and ranges and references
new RandExp(/<([a-z]\w{0,20})>foo<\1>/).gen();
// => foo
// wildcard
new RandExp(/random stuff: .+/).gen();
// => random stuff: l3m;Hf9XYbI [YPaxV>U*4-_F!WXQh9>;rH3i l!8.zoh?[utt1OWFQrE ^~8zEQm]~tK
// ignore case
new RandExp(/xxx xtreme dragon warrior xxx/i).gen();
// => xxx xtReME dRAGON warRiOR xXX
// dynamic regexp shortcut
new RandExp('(sun|mon|tue|wednes|thurs|fri|satur)day', 'i');
// is the same as
new RandExp(new RegExp('(sun|mon|tue|wednes|thurs|fri|satur)day', 'i'));
```
If you're only going to use `gen()` once with a regexp and want slightly shorter syntax for it
```js
const randexp = require('randexp').randexp;
randexp(/[1-6]/); // 4
randexp('great|good( job)?|excellent'); // great
```
If you miss the old syntax
```js
require('randexp').sugar();
/yes|no|maybe|i don't know/.gen(); // maybe
```
# Motivation
Regular expressions are used in every language, every programmer is familiar with them. Regex can be used to easily express complex strings. What better way to generate a random string than with a language you can use to express the string you want?
Thanks to [String-Random](http://search.cpan.org/~steve/String-Random-0.22/lib/String/Random.pm) for giving me the idea to make this in the first place and [randexp](https://github.com/benburkert/randexp) for the sweet `.gen()` syntax.
# Default Range
The default generated character range includes printable ASCII characters.
In order to add or remove characters,
a `defaultRange` attribute is exposed. you can `subtract(from, to)` and `add(from, to)`
```js
const randexp = new RandExp(/random stuff: .+/);
randexp.defaultRange.subtract(32, 126);
randexp.defaultRange.add(0, 65535);
randexp.gen();
// => random stuff: 湐箻ໜ䫴㳸長���邓蕲뤀쑡篷皇硬剈궦佔칗븛뀃匫鴔事좍ﯣ⭼ꝏ䭍詳蒂䥂뽭
```
You can also change the default range by changing `RandExp.prototype.defaultRange`.
# Custom PRNG
The default randomness is provided by `Math.random()`. If you need to use a seedable or cryptographic PRNG, you
can override `RandExp.prototype.randInt` or `randexp.randInt` (where `randexp` is an instance of `RandExp`). `randInt(from, to)` accepts an inclusive range and returns a randomly selected number within that range.
# Infinite Repetitionals
Repetitional tokens such as `*`, `+`, and `{3,}` have an infinite max range. In this case, randexp looks at its min and adds 100 to it to get a useable max value. If you want to use another int other than 100 you can change the `max` property in `RandExp.prototype` or the RandExp instance.
```js
const randexp = new RandExp(/no{1,}/);
randexp.max = 1000000;
```
With `RandExp.sugar()`
```js
const regexp = /(hi)*/;
regexp.max = 1000000;
```
# Bad Regular Expressions
There are some regular expressions which can never match any string.
* Ones with badly placed positionals such as `/a^/` and `/$c/m`. Randexp will ignore positional tokens.
* Back references to non-existing groups like `/(a)\1\2/`. Randexp will ignore those references, returning an empty string for them. If the group exists only after the reference is used such as in `/\1 (hey)/`, it will too be ignored.
* Custom negated character sets with two sets inside that cancel each other out. Example: `/[^\w\W]/`. If you give this to randexp, it will return an empty string for this set since it can't match anything.
# Projects based on randexp.js
## JSON-Schema Faker
Use generators to populate JSON Schema samples. See: [jsf on github](https://github.com/json-schema-faker/json-schema-faker/) and [jsf demo page](http://json-schema-faker.js.org/).
# Install
### Node.js
npm install randexp
### Browser
Download the [minified version](https://github.com/fent/randexp.js/releases) from the latest release.
# Tests
Tests are written with [mocha](https://mochajs.org)
```bash
npm test
```
# Integration with TypeScript
RandExp includes TypeScript definitions.
```typescript
import RandExp from "randexp";
const randexp = new RandExp(/[a-z]{6}/);
randexp.gen();
```
Use dtslint to check the definition file.
npm install -g dtslint
npm run dtslint