Factory Implementation

Introduction

A Factory centralizes object creation logic, hiding the instantiation details from the caller.

Simple Factory Function

class User { constructor(name) { this.name = name; this.role = 'user'; } }
class Admin { constructor(name) { this.name = name; this.role = 'admin'; } }
class Guest { constructor(name) { this.name = name; this.role = 'guest'; } }

function userFactory(type, name) {
  switch (type) {
    case 'admin': return new Admin(name);
    case 'guest': return new Guest(name);
    default: return new User(name);
  }
}

const alice = userFactory('admin', 'Alice');
const bob = userFactory('user', 'Bob');

Factory with Configuration

function createApiClient(config) {
  const baseURL = config.baseURL;
  const headers = { 'Content-Type': 'application/json', ...config.headers };

  return {
    async get(endpoint) {
      const res = await fetch(`${baseURL}${endpoint}`, { headers });
      return res.json();
    },
    async post(endpoint, data) {
      const res = await fetch(`${baseURL}${endpoint}`, {
        method: 'POST', headers, body: JSON.stringify(data)
      });
      return res.json();
    }
  };
}

const api = createApiClient({ baseURL: 'https://api.example.com' });

Summary

Factory functions centralize object creation
Hides complex instantiation logic
Easy to extend with new types
Useful for API clients, model creation, and dependency injection

Factory Implementation

Factory Implementation

Introduction

Simple Factory Function

Factory with Configuration

Summary

Further Reading