How do let, const, and var differ in scope and reassignment?

let and const are block-scoped, while var is function-scoped or script-global depending on context. const prevents reassigning the binding, but it does not make a referenced object immutable. let permits reassignment. Accessing a let or const binding before initialization throws because it is in the temporal dead zone. var declarations are initialized to undefined before their assignment executes. Prefer const when the binding will not change and let when reassignment is intentional; understanding scope matters more than treating the keywords as interchangeable style choices.