Scope

Summary

The rules that determine where a variable is accessible — global, function and block scope — and how nested scopes can 'see' outer variables. Scope is closely connected to closures, modules, debugging, and variable lifetime, making it one of the most important concepts for understanding non-trivial JavaScript.

• 1Nest functions and log which outer variables each inner function can access. Validate your understanding by applying it in a small practical example.
• 2Compare block scope (`let`/`const`) vs function scope (`var`). Write down when you would choose each option and what trade-off drives that choice.
• 3Learn lexical scoping — scope is determined by where code is written, not called.