Variables

Var Keyword

Can be reassigned and are only available inside the function they're created in. Its function scoped.

var variableName = value;

Let Keyword

It can be reassinged but its similar to const i.e. block scoped.

let variableName = value;

Const Keyword

Cannot be reassigned and not accessible before they appear within the code. Its block scoped.

const variableName = value;

Keyword	scope	Redeclared (within the scope)
var	Global or Functional scope	Yes
let	Block scope (inside {})	No
const	Block scope (inside {})	No

---

What is the block ?

A block is a set of opening and closing curly brackets.