Difference between var, let and const in JavaScript

Introduction to JavaScript Variables

JavaScript offers 3 distinct ways to declare variables:

• var
• let
• const

Description

1. var is the oldest way to declare variables in JavaScript, originating from its earliest versions
2. let provides block-level scope, offering more predictable behavior and reducing the risk of errors associated with var.
3. const is used to declare variables meant to be constants, meaning their value should not change after the initial assignment.

Key Differences

Scope:

• var: Function scope.
• let and const: Block scope.

Hoisting:

• var: Hoisted and initialized to undefined.
• let and const: Hoisted but not initialized, resulting in a temporal dead zone.

Reassignment:

• var and let: Can be reassigned.
• const: Cannot be reassigned after initial assignment.

Redeclaration:

• var: Can be redeclared in the same scope.
• let and const: Cannot be redeclared in the same scope.