throw syntax in Javascript

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?

The console says it clearly in chrome: Uncaught SyntaxError: Illegal newline after throw It is the line break that is the problem. Add a space and it would work throw { It does not have to be attached. — epascarello
– epascarello, Commented Jan 9, 2015 at 4:56
the same thing return statement is also affected.. Its Automatic semicolon insertion. stackoverflow.com/a/27738985/3556874 — Naeem Shaikh
– Naeem Shaikh, Commented Jan 9, 2015 at 5:17
@epascarello please read the question once again, I don't think you are getting me.The space given or not given doesn't matter,what matters is that the { should be in the same line. The { bracked attached together works perfectly. — suman
– suman, Commented Jan 9, 2015 at 5:20
I know what the problem is.... The error message that chrome gives was the answer. And there a few things in JS that can not have a line break after them. You found one of them. — epascarello
– epascarello, Commented Jan 9, 2015 at 5:22

Community · Accepted Answer · 2017-05-23 10:33:19Z

6

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.

edited May 23, 2017 at 10:33

CommunityBot

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answered Jan 9, 2015 at 4:53

BoltClock

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