All 10 Design Patterns in JavaScript questions
More in Design Patterns in JavaScript
What is the Singleton pattern and how is it implemented in JavaScript? How do you implement the Observer pattern in JavaScript? What is the Factory pattern, and how does it differ from calling a class constructor directly? How is the Decorator pattern typically implemented in JavaScript? What is the Strategy pattern and how does it help avoid large if/else chains? How do you implement the Proxy pattern using JavaScript's built-in Proxy object? What is the Command pattern and where is it useful in JavaScript apps? What is the Adapter pattern and why is it useful when integrating third-party code? When is it a mistake to force a 'classic' design pattern into idiomatic JavaScript?
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What is the Module pattern and what problem does it solve?

Beginner

Answer

The Module pattern uses a function closure (or an ES module) to keep internal variables private and expose only a controlled public API, preventing external code from directly manipulating internal state.
const counter = (function () {
  let count = 0;
  return {
    increment: () => ++count,
    get: () => count
  };
})();
counter.increment();
console.log(counter.get()); // 1
Real-world example Building a small state-tracking utility without leaking its internal variable to the global scope.

Common follow-ups: How do native ES modules make the classic IIFE module pattern less necessary today?

Scope Hoisting & Closures
All 10 Design Patterns in JavaScript questions