4 Practical Applications of Closures in JavaScript

When I first learned about closures, I thought they were rarely used and that I probably wouldn’t come across them often. What I didn’t realise then was that every time a function is created, a closure is formed automatically, because a function maintains a reference to its lexical environment.

Closures are not just a theoretical concept. They are everywhere in our codebase, and they have powerful real-world use cases. Understanding these use cases, I believe, is crucial to truly understanding closures.

Let’s look at four powerful applications of closures.

1. Data Privacy & Encapsulation

Closures help you create private variables in JavaScript, preventing accidental modifications and protecting internal state.

2. Function Factories

Closures make it possible to build tailored functions on demand. This pattern works especially well with the Fetch API, where you can create reusable and pre-configured API clients.

3. Preserving State in Callbacks & Event Handlers

Closures are crucial for managing state in asynchronous operations. When you use addEventListener() to register an event handler, the callback retains access to variables from its outer scope.

4. Memoization (Caching Results)

Closures can be used to memoize expensive operations by caching previous results. This improves performance by avoiding repeated calculations.

What once felt like an abstract concept turned out to be one of the most practical tools in JavaScript. The real power of closures isn’t in their definition — it’s in how often and how effectively we use them.

Happy Learning!✨