What is the difference between var, let and const?

Answer

var is function-scoped and hoisted as undefined, so it's readable before its declaration and leaks out of blocks. let and const are block-scoped and sit in the temporal dead zone until declared, so reading them early throws. const additionally prevents reassignment of the binding — it does not freeze the value, so a const object's properties can still change.

Points an interviewer listens for

• var: function-scoped, hoisted as undefined
• let/const: block-scoped, temporal dead zone
• const blocks reassignment, not mutation
• Default to const, reach for let when you must reassign

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