@night_slayer/fake-js

A lightweight, enterprise-grade fake data generator for development and testing. Now with TypeScript support, seeded randomness, and a flexible API.

Features

• 🔒 Type Safe: Written in TypeScript with full type definitions.
• 🧠 Smart Consistency: Emails match names (e.g., "John Doe" -> "[email protected]").
• 📅 Dynamic Dates: Generates realistic past, future, and birth dates.
• 🎲 Deterministic: Support for seeded randomness for reproducible tests.
• 🌍 Localization: Support for 10+ locales (en, es, fr, de, it, pt, ru, ja, zh, hi).
• 🛠️ CLI Tool: Generate data directly from the command line.
• 🔌 Extensible: Add custom data generators easily.
• 📦 Tree Shakeable: Granular access to data generators.
• ⚡ Fast: Lightweight and efficient.
• 📚 Rich Data: Over 100+ items per category for each locale.

Installation

npm install @night_slayer/fake-js

Usage

Basic Usage

Import the Faker class and create an instance to generate data.

import { Faker } from '@night_slayer/fake-js';

const faker = new Faker();

// Generate a single user object
const user = faker.createUser();
console.log(user);
/*
{
  id: 1,
  name: 'John Doe',
  email: '[email protected]',
  birthdate: 1990-05-15T00:00:00.000Z,
  ...
}
*/

// Generate multiple users
const users = faker.createUsers(5);

Deterministic Data (Seeding)

Pass a seed to the constructor to generate the same data every time. This is perfect for unit tests that need to be consistent.

const faker = new Faker({ seed: 123 });

console.log(faker.person.name()); // Always the same name for seed 123

Localization

Initialize Faker with a locale to generate localized data.

// Generate Spanish data
const faker = new Faker({ locale: 'es' });

console.log(faker.person.name()); // "Juan Perez"
console.log(faker.location.city()); // "Madrid"

Supported locales: en, es, fr, de, it, pt, ru, ja, zh, hi.

Granular Access & Consistency

You can access specific data generators directly.

const faker = new Faker();

// Smart Consistency
const name = faker.person.name();
const email = faker.internet.email(name); // "[email protected]"

// Dynamic Dates
const past = faker.date.past();   // Random date in past year
const future = faker.date.future(); // Random date in future year
const birthdate = faker.person.birthdate({ min: 18, max: 65 }); // Age 18-65

console.log(faker.phone.number());
console.log(faker.location.city());

Extensibility

Add your own custom data generators.

const faker = new Faker();

faker.addGenerator('customId', () => `ID-${Math.random()}`);

const user = faker.createUser();
console.log(user.customId); // "ID-0.123..."

CLI Usage

Generate data directly from your terminal.

# Generate 5 users with French locale
npx fake-js --count 5 --locale fr

# Save to file
npx fake-js --count 100 > users.json

API Reference

new Faker(options?)

• options.seed (optional): A number or string to seed the random number generator.
• options.locale (optional): The locale to use (default: 'en').

Methods

• createUser(id?: number): User: Generates a complete user object with consistent data.
• createUsers(count?: number): User[]: Generates an array of user objects.

Modules

• faker.person: name(), birthdate(options?), educationLevel(), hobby()
• faker.internet: email(name?)
• faker.date: past(years?), future(years?), between(from, to)
• faker.phone: number()
• faker.location: city(), address()
• faker.work: jobTitle(), companyName(), skill(), skills(count)

License

MIT