The JavaScript uses the lexical scoping of variables. Simply the placement of the variable will determine who can access it. The access to the variable does not depend on how and when the code runs. Javascript determines the access of variables at compile time itself.

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Hierarchy of Scope In Javascript

• Global Scope This are the variables which are accessible by all functions. We define them at the outermost place in our code structure.
• Function Scope These are the variables which we define inside the function (With var keyword). They are only accessible inside the function and children functions in which we define the variable.
• Block Scope The ES6 module provides us the block scope variable. These are the variables which we define inside any pair of curly braces { }. (using keywords let and const).