What is the difference between closures and block-scoped variables?

What is the difference between closures and block-scoped variables?

Closures are functions that remember their lexical scope even when the function is executed outside that scope. Block-scoped variables, introduced in ES6, are variables declared with let and const that are limited to the block in which they are defined.

Can you give me an example of a closure?

Sure! Here's a simple example:

function outerFunction() {
    let outerVariable = 'I am outside!';
    function innerFunction() {
        console.log(outerVariable);
    }
    return innerFunction;
}

const closureExample = outerFunction();
closureExample(); // Outputs: I am outside!

How do block-scoped variables work?

Block-scoped variables are declared using let or const. They only exist within the nearest enclosing block (like a loop or an if statement). For example:

if (true) {
    let blockVariable = 'I am block-scoped!';
    console.log(blockVariable);
}
console.log(blockVariable); // ReferenceError: blockVariable is not defined

What are the practical uses of closures?

Closures are useful for data encapsulation, creating private variables, and implementing function factories. They help maintain state in asynchronous programming and event handling.