Understanding Scope Javascript

A simple definition for a scope in 

Scope is that the accessibility of variables, functions, and objects in some particular a part of your     code during runtime. In other words, scope determines the visibility of variables and other resources in     areas of your code.

    As per the above definition of Scope, So, the purpose in limiting the visibility of variables and not         having everything available everywhere in your code.

    the scope is defined within the main two ways,

• Global Scope
• Local Scope

var greeting='Welcome to blog';
(function(){
  console.log(greeting); //Output: Welcome to blog
})();

consider above code greeting variable should be global scope, it can access inside the function,

(function(){var greeting = 'Welcome to blog';
  console.log(greeting); //Output: Welcome to blog
})();console.log(greeting); //Output:Reference-Error greeting not defined

In the above code for local scope,

In scope level variables in JavaScript ES6 has updated hoisting variable let, var, const type check with that, In order to learn the scope, you need to understand hoisting also.