juniorJavaScript
What is the difference between var, let, and const?
Updated May 6, 2026
Short answer
var is function-scoped, while let and const are block-scoped. const cannot be reassigned.
Deep explanation
var is hoisted and can be redeclared. let and const are block-scoped and exist in the temporal dead zone until declared. const ensures binding immutability.
Real-world example
Use const for API configs, let for loop counters.
Common mistakes
- Assuming const makes objects immutable.
Follow-up questions
- What is hoisting?
- Can const objects be mutated?