用Javascript抛出语法

Question

How is

    throw
       {
         name: 'type error',
         message: 'provide numeric value'
       };

a incorrect syntax when

    throw{
         name: 'type error',
         message: 'provide numeric value'
       };

Is a correct syntax?

Is it really necessary to attach curly bracket with throw and why?

Answer 1

For some reason, a semicolon is always inserted after a lone throw keyword even though you can't legally have a throw statement by itself, so what you get is this:

    throw;
       {
         name: 'type error',
         message: 'provide numeric value'
       };

which results in a syntax error.

For what it's worth, C# (which, like JS, is also based on an ECMA standard) does support throw; statements as a way to rethrow an exception . Perhaps they're futureproofing ECMAScript for support for a similar feature down the road. But this is just conjecture on my part.