Which statement about var, let, and const in JavaScript is true?

Which statement about var, let, and const in JavaScript is true?

• A. Var is block-scoped and cannot be redeclared.
• B. Var is function-scoped and can be redeclared; let and const are block-scoped, with let mutable and const read-only bindings.
• C. Let is function-scoped and immutable.
• D. Const is block-scoped and can be redeclared.

Answer: (B)

Understanding how JavaScript binds variables hinges on scope and mutability. Var is scoped to the containing function (or global if outside any function) and can be redeclared within that scope, which is why you can have multiple var declarations in the same function and they all refer to the same binding. Let and const introduce block scope, meaning their bindings exist only inside the nearest set of braces. Let allows reassignment, so you can change its value; const does not allow reassignment of the binding after it’s initialized. However, if the value is an object or array, you can still modify its contents; you just can’t replace the binding with a new object or array.

This combination—var being function-scoped and redeclarable; let and const being block-scoped, with let being mutable and const binding being read-only for reassignment—matches how these declarations actually behave, so it’s the correct description.