scope and closures

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Scope

• refers to where in your code a given variable or function can be accessed during runtime

Global scope

• only one global scope throughout a JS document
• variable is global if it's declared outside of a function
• globally-scoped variables can be accessed and altered in any other scope

Local scope

• variable is locally-scoped if it's declared inside a function
• locally-scoped variables can only be accessed from within the function they are declared in and other functions that may be enclosed within the parent function

Block scope

• const and let can create block-scoped variables
• block statement: delimited by pair of curly braces; if and switch conditions, for and while loops
• block-scoped variables can only be accessed from within the block statement they are declared in

Tips/gotchas

• never use undeclared variables--you will unintentionally create global variables and clutter up the global scope

Closures