What are the differences between scope and closure in JavaScript?

What are the differences between scope and closure in JavaScript?

Scope refers to the visibility of variables in different parts of your code, while closure is a function that retains access to its lexical scope even when the function is executed outside that scope.

Can you give me an example of scope?

Sure! In JavaScript, if you declare a variable inside a function, it is only accessible within that function. For example:

function myFunction() {
    var localVar = 'I am local';
    console.log(localVar);
}
myFunction(); // Outputs: I am local
console.log(localVar); // ReferenceError: localVar is not defined

And what about closure?

A closure is created when a function retains access to its outer scope even after the outer function has finished executing. Here's an example:

function outerFunction() {
    var outerVar = 'I am outside!';
    function innerFunction() {
        console.log(outerVar);
    }
    return innerFunction;
}
var myInnerFunction = outerFunction();
myInnerFunction(); // Outputs: I am outside!

That's really helpful! How do I know when to use closures?

You should use closures when you need to maintain state in an asynchronous environment or when you want to encapsulate variables to avoid polluting the global scope.