Question 1

What error does re-declaring let in the same scope throw in JavaScript?

Accepted Answer

SyntaxError: Identifier 'x' has already been declared. The engine catches the duplicate declaration at parse time, before any code runs.

Question 2

What is the difference between SyntaxError, ReferenceError, and TypeError in JavaScript?

Accepted Answer

SyntaxError is caught at parse time (malformed code, const without initializer, re-declaration). ReferenceError is at runtime (variable does not exist or is in TDZ). TypeError is at runtime (value is wrong type for the operation, reassigning const).

Question 3

Why does const without an initializer throw SyntaxError not ReferenceError?

Accepted Answer

Because the engine catches it during parsing, before any code runs. 'const x;' is malformed syntax (const requires an initializer), so it is a SyntaxError, not a runtime ReferenceError.

Question 4

Why does reassigning a const throw TypeError not ReferenceError in JavaScript?

Accepted Answer

Because the variable exists (no ReferenceError), but the operation (assignment) is not allowed for a const. The value's type (const binding) does not support reassignment, so it is a TypeError.

What error does re-declaring let in the same scope throw in JavaScript?

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