135 lines
4.3 KiB
Markdown
135 lines
4.3 KiB
Markdown
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# randexp.js
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randexp will generate a random string that matches a given RegExp Javascript object.
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[](http://travis-ci.org/fent/randexp.js)
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[](https://david-dm.org/fent/randexp.js)
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[](https://codecov.io/gh/fent/randexp.js)
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# Usage
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```js
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var RandExp = require('randexp');
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// supports grouping and piping
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new RandExp(/hello+ (world|to you)/).gen();
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// => hellooooooooooooooooooo world
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// sets and ranges and references
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new RandExp(/<([a-z]\w{0,20})>foo<\1>/).gen();
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// => <m5xhdg>foo<m5xhdg>
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// wildcard
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new RandExp(/random stuff: .+/).gen();
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// => random stuff: l3m;Hf9XYbI [YPaxV>U*4-_F!WXQh9>;rH3i l!8.zoh?[utt1OWFQrE ^~8zEQm]~tK
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// ignore case
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new RandExp(/xxx xtreme dragon warrior xxx/i).gen();
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// => xxx xtReME dRAGON warRiOR xXX
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// dynamic regexp shortcut
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new RandExp('(sun|mon|tue|wednes|thurs|fri|satur)day', 'i');
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// is the same as
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new RandExp(new RegExp('(sun|mon|tue|wednes|thurs|fri|satur)day', 'i'));
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```
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If you're only going to use `gen()` once with a regexp and want slightly shorter syntax for it
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```js
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var randexp = require('randexp').randexp;
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randexp(/[1-6]/); // 4
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randexp('great|good( job)?|excellent'); // great
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```
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If you miss the old syntax
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```js
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require('randexp').sugar();
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/yes|no|maybe|i don't know/.gen(); // maybe
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```
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# Motivation
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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?
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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.
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# Default Range
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The default generated character range includes printable ASCII. In order to add or remove characters,
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a `defaultRange` attribute is exposed. you can `subtract(from, to)` and `add(from, to)`
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```js
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var randexp = new RandExp(/random stuff: .+/);
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randexp.defaultRange.subtract(32, 126);
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randexp.defaultRange.add(0, 65535);
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randexp.gen();
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// => random stuff: 湐箻ໜ䫴㳸長<E3B3B8><E995B7><EFBFBD>邓蕲뤀쑡篷皇硬剈궦佔칗븛뀃匫鴔事좍ﯣ⭼ꝏ䭍詳蒂䥂뽭
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```
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# Custom PRNG
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The default randomness is provided by `Math.random()`. If you need to use a seedable or cryptographic PRNG, you
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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
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number within that range.
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# Infinite Repetitionals
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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.
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```js
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var randexp = new RandExp(/no{1,}/);
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randexp.max = 1000000;
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```
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With `RandExp.sugar()`
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```js
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var regexp = /(hi)*/;
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regexp.max = 1000000;
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```
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# Bad Regular Expressions
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There are some regular expressions which can never match any string.
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* Ones with badly placed positionals such as `/a^/` and `/$c/m`. Randexp will ignore positional tokens.
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* 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.
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* 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.
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# Projects based on randexp.js
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## JSON-Schema Faker
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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/).
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# Install
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### Node.js
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npm install randexp
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### Browser
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Download the [minified version](https://github.com/fent/randexp.js/releases) from the latest release.
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# Tests
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Tests are written with [mocha](https://mochajs.org)
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```bash
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npm test
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```
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# License
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MIT
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