Encapsulating State using Closures

Snippet

Encapsulating State using Closures

Closures allow a function to 'remember' the environment in which it was created. Here, the variable 'count' is inaccessible from the outside world, providing a pattern for private state without classes.

snippet.js
javascript
function createSecureCounter() {
  let count = 0;
  return {
    increment: () => ++count,
    getCount: () => count
  };
}
 
const counter = createSecureCounter();
console.log(counter.increment()); // 1
// console.log(count); // ReferenceError

Breakdown

let count = 0;

A local variable defined within the scope of the outer function.

return { increment: ... };

Returns an object containing functions that still have access to the local variable.

const counter = createSecureCounter();

Creates an instance where the 'count' state is preserved across calls.

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Encapsulating State using Closures

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