What Is the Difference Between var, let, and const?

What Is the Difference Between var, let, and const?

JavaScript provides three ways to declare variables:

• var
• let
• const

Understanding their differences is important for writing reliable code.

var

Variables declared with var:

• Are Function Scoped
• Can Be Redeclared
• Can Be Reassigned
• Are Hoisted

Example:

var name = "John";
var name = "Jane";

The redeclaration is allowed.

let

Variables declared with let:

• Are Block Scoped
• Cannot Be Redeclared In The Same Scope
• Can Be Reassigned

Example:

let age = 25;
age = 26;

Reassignment is allowed.

const

Variables declared with const:

• Are Block Scoped
• Cannot Be Redeclared
• Cannot Be Reassigned

Example:

const PI = 3.14;

The variable reference cannot be changed.

Scope Comparison

Block scope means variables only exist inside the block where they are declared.

This behavior helps prevent accidental bugs.

Which One Should You Use?

A common recommendation is:

• Use const by default.
• Use let when reassignment is required.
• Avoid var in modern JavaScript.

The Bottom Line

let and const are generally preferred over var because they provide block scope and help developers write safer, more predictable code.