randexp vs faker vs chance vs casual
JavaScript Data Generation Libraries Comparison
1 Year
randexpfakerchancecasualSimilar Packages:
What's JavaScript Data Generation Libraries?

Data generation libraries in JavaScript are essential tools for developers who need to create realistic test data for applications, prototypes, or simulations. These libraries provide a variety of functions to generate random data, such as names, addresses, dates, and even complex data structures. By using these libraries, developers can streamline the testing process, ensure data consistency, and avoid the pitfalls of hardcoded values in their applications. Each library has its unique features and strengths, making them suitable for different use cases in data generation.

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randexp4,388,9591,839-137 years agoMIT
faker2,234,544-10.1 MB--MIT
chance1,799,9116,5102.13 MB1768 months agoMIT
casual197,0833,021-426 years agoMIT
Feature Comparison: randexp vs faker vs chance vs casual

Data Variety

  • randexp:

    Randexp specializes in generating random strings based on user-defined regular expressions. This allows for highly customizable data generation, particularly for testing input fields.

  • faker:

    Faker excels in generating realistic and diverse data, including user profiles, product information, and company details. It supports multiple locales, allowing for localized data generation.

  • chance:

    Chance offers a wide variety of data types, including names, addresses, phone numbers, and even custom data types. It supports statistical distributions, making it ideal for generating diverse datasets.

  • casual:

    Casual provides a limited range of data types, focusing on simple random values such as names, addresses, and dates. It is suitable for basic use cases where complex data structures are not required.

Ease of Use

  • randexp:

    Randexp is straightforward for those familiar with regular expressions. However, it may be challenging for developers who are not comfortable with regex syntax, as it requires understanding how to define patterns.

  • faker:

    Faker is user-friendly but may require a bit more setup compared to Casual. Its extensive documentation and examples make it easier to get started with generating complex datasets.

  • chance:

    Chance has a slightly steeper learning curve than Casual but is still user-friendly. Its extensive documentation helps developers understand how to utilize its features effectively.

  • casual:

    Casual is designed for simplicity, making it easy to use for developers of all skill levels. Its straightforward API allows for quick integration into projects without a steep learning curve.

Localization Support

  • randexp:

    Randexp does not focus on localization, as it primarily generates random strings based on regex patterns. Its use is more about format validation than localized data generation.

  • faker:

    Faker provides extensive localization support, enabling developers to generate data in various languages and formats. This is particularly beneficial for applications targeting international users.

  • chance:

    Chance supports multiple locales, allowing developers to generate data that is culturally relevant and appropriate for different regions, enhancing its usability in global applications.

  • casual:

    Casual has limited localization support, primarily focusing on English data generation. It may not be suitable for applications requiring data in multiple languages or regions.

Performance

  • randexp:

    Randexp is efficient for generating random strings based on regex but may become slower with highly complex patterns. Its performance is generally good for most use cases.

  • faker:

    Faker can be slower than other libraries when generating large amounts of data due to its focus on realism and complexity. Performance can be improved by generating data in batches or using asynchronous methods.

  • chance:

    Chance is efficient for generating random data and can handle larger datasets without significant performance issues, making it suitable for more extensive testing scenarios.

  • casual:

    Casual is lightweight and performs well for generating small amounts of data. However, it may not be optimized for generating large datasets quickly.

Extensibility

  • randexp:

    Randexp is specialized for regex-based data generation and does not offer extensibility in the traditional sense. However, developers can create custom regex patterns to suit their needs.

  • faker:

    Faker is highly extensible, allowing developers to create custom data generators and extend its functionality. This makes it suitable for complex applications with unique data requirements.

  • chance:

    Chance allows for some level of extensibility, enabling developers to create custom data generators if needed, but it is primarily designed to work out of the box.

  • casual:

    Casual is not highly extensible, as it focuses on providing a simple set of features. Customization options are limited compared to other libraries.

How to Choose: randexp vs faker vs chance vs casual
  • randexp:

    Use Randexp if your primary need is to generate random strings that conform to specific regular expressions. This is particularly useful for testing input validation and ensuring that your application can handle various data formats.

  • faker:

    Opt for Faker if you want a robust library that can generate a vast array of realistic data, including names, addresses, and even entire user profiles. It is particularly useful for applications that require extensive data for testing and development.

  • chance:

    Select Chance if you require a more comprehensive set of data generation options with a focus on randomness and statistical distributions. It is suitable for projects that need a wide variety of data types and formats.

  • casual:

    Choose Casual if you need a simple and straightforward library for generating random data without complex configurations. It is user-friendly and ideal for quick prototypes or small projects.

README for randexp

randexp.js

randexp will generate a random string that matches a given RegExp Javascript object.

Build Status Dependency Status codecov

Usage

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();
// => <m5xhdg>foo<m5xhdg>

// 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

const randexp = require('randexp').randexp;

randexp(/[1-6]/); // 4
randexp('great|good( job)?|excellent'); // great

If you miss the old syntax

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 for giving me the idea to make this in the first place and randexp for the sweet .gen() syntax.

Default Range

The default generated character range includes printable ASCII. In order to add or remove characters, a defaultRange attribute is exposed. you can subtract(from, to) and add(from, to)

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.

const randexp = new RandExp(/no{1,}/);
randexp.max = 1000000;

With RandExp.sugar()

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 and jsf demo page.

Install

Node.js

npm install randexp

Browser

Download the minified version from the latest release.

Tests

Tests are written with mocha

npm test

Integration with TypeScript

RandExp includes TypeScript definitions.

import * as 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