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javascriptecmascript-6arrow-functions

Why is `throw` invalid in an ES6 arrow function?

I'm just looking for a reason as to why this is invalid:

() => throw 42;

I know I can get around it via:

() => {throw 42};
Solution

  • If you don't use a block ({}) as body of an arrow function, the body must be an expression:

    ArrowFunction:
    ArrowParameters[no LineTerminator here] => ConciseBody

ConciseBody:
    [lookahead ≠ { ] AssignmentExpression
    { FunctionBody }

    But throw is a statement, not an expression.

    In theory

    () => throw x;

    is equivalent to

    () => { return throw x; }

    which would not be valid either.