What are some practical use cases for JavaScript closures?

What are some practical use cases for JavaScript closures?

JavaScript closures are often used for data encapsulation, creating private variables, and maintaining state in asynchronous functions.

Can you give me an example of using closures for data encapsulation?

Sure! You can create a function that returns another function, allowing you to keep certain variables private. For instance:

function createCounter() {
    let count = 0;
    return function() {
        count++;
        return count;
    };
}
const counter = createCounter();
console.log(counter()); // 1
console.log(counter()); // 2

This way, count is not accessible from outside the createCounter function.

What about using closures in asynchronous programming?

Closures are useful in asynchronous programming to maintain access to variables from the outer function. For example:

function fetchData() {
    let data = 'Initial Data';
    setTimeout(function() {
        data = 'Updated Data';
        console.log(data);
    }, 1000);
    console.log(data);
}
fetchData();

Here, the inner function retains access to the data variable even after the outer function has executed.