What are scope chains in JavaScript?

Can you explain what scope chains are in JavaScript?

Sure! In JavaScript, a scope chain is a series of scopes that the engine uses to look up variables. When a variable is referenced, the JavaScript engine checks the current scope first, and if it doesn't find the variable there, it moves up to the outer scope, continuing until it reaches the global scope.

How does the scope chain affect variable access?

The scope chain determines the accessibility of variables. If a variable is defined in an outer scope, inner functions can access it due to the scope chain. However, if a variable is not found in any of the scopes, it results in a reference error.

Can you give an example of a scope chain?

Absolutely! Consider this code:

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

Here, innerFunction can access outerVar because of the scope chain.

What happens if I try to access a variable that is not in the scope chain?

If you try to access a variable that isn't in the scope chain, JavaScript will throw a ReferenceError, indicating that the variable is not defined.