What is scope chaining in JavaScript?

What is scope chaining in JavaScript?

Scope chaining is a mechanism that allows JavaScript to look up variables in nested scopes. When a variable is referenced, JavaScript first checks the current scope, then moves up to the outer scope, and continues until it finds the variable or reaches the global scope.

Can you give me an example of scope chaining?

Sure! Consider this code:

function outerFunction() {
    let outerVar = 'I am from outer scope';
    function innerFunction() {
        console.log(outerVar);
    }
    innerFunction();
}
outerFunction();

In this example, innerFunction can access outerVar due to scope chaining.

What happens if a variable is not found in any scope?

If a variable is not found in any scope, JavaScript will throw a ReferenceError, indicating that the variable is not defined.

How does scope chaining relate to closures?

Scope chaining is fundamental to closures. A closure is created when a function retains access to its lexical scope, even when the function is executed outside that scope. This means inner functions can access variables from their outer functions.