What is the difference between var, let, and const?

Answer

Feature	var	let	const
Scope	Function	Block	Block
Hoisting	Yes (undefined)	Yes (TDZ)	Yes (TDZ)
Reassign	✅	✅	❌
Redeclare	✅	❌	❌

Example

var a = 1;
var a = 2; // OK

let b = 1;
// let b = 2; // Error: already declared

const c = 1;
// c = 2; // Error: assignment to constant

Key Points

• Use const by default
• Use let when you need to reassign
• Avoid var in modern JavaScript