What is the difference between let, const, and var when declaring variables in JavaScript?

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Ravi Vishwakarma · Answer

let, const, and var keywords are used for variable declarations, but they have some key differences in terms of scope, hoisting, and mutability var: Function-scoped or globally scoped: Variables declared with var are function-scoped when declared inside a function, or globally scoped when declared outside any function.Hoisting: Variables declared with var are hoisted to the top of their scope and initialized with undefined. This means you can use a var variable before it's declared in the code.Reassignment and redeclaration: Variables declared with var can be redeclared and reassigned. let: Block-scoped: Variables declared with let have block scope, which means they are only accessible within the nearest enclosing curly braces { }.Hoisting: Variables declared with let are hoisted to the top of their block but are not initialized. This means you cannot access a let variable before it's declared in the code.Reassignment but not redeclaration: Variables declared with let can be reassigned, but you cannot redeclare them in the same scope. const: Block-scoped: Like let, variables declared with const have block scope.Hoisting: Variables declared with const are also hoisted to the top of their block but are not initialized. You cannot access a const variable before it's declared.Immutable reference: Variables declared with const must be initialized with a value and cannot be reassigned to a different reference. However, their value may be mutable (e.g., properties of an object or elements of an array can be changed).

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What is the difference between let, const, and var when declaring variables in JavaScript?

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var:

let:

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