Scope

Scope is what we can access and where we can access it. It is the concept of where something is available.

Through the scope chain, a function has access to all variables and functions declared in its outer scope.

3 levels of scope

Global

• Accessible in every scope
• Outermost scope

Functional

• Accessible within a function
• If you have 2 functions, they have their own unique scopes. You can't access the same items from each other's boxes.
• Specific to a single function
• Can't be accessed by anything in outer scopes
• Every function creates its own scope, and any variables or functions you declare inside of the function will not be available outside of it.

Block

• Accessible within a block
• Specific blocks
• Can't be accessed by anything in outer scopes
• Variables declared with var are not block scoped. Variables declared with const and let are block scoped.

Lexical Scope

• Can access variables in outer scope
• Can't access variable in nested scope

Cannot access variables in parent scope.