Throwing an Error inside the context of a closure is not reaching the catch clause

Question

I am throwing an exception in the context of closure and can't catch it. Here is a trivial example.

try{
  setTimeout(function(){ throw Error() },100)
}
catch(error)
{
   console.log("YES",error);
}

It never makes it to the catch clause and causes my node process to terminate. Same issue here:

try{
  setTimeout(function(){undefinedMethod() },100)
}
catch(error)
{
   console.log("YES",error);
}

My real example is closer to this:

 try{
   var ctx={setTimeout:setTimeout};
   require('vm').runInNewContext("setTimeout(function(){undefinedMethod() },100)",ctx)  
 }
 catch(error)
 {
   console.log(error);
 }

I need the try/catch as safety measure. Currently this behaviour causes my node process to terminate. How can I catch the exception?

What about putting the try/catch inside the timeout? – evolutionxbox Jul 28 '15 at 10:29 — evolutionxbox, Jul 28 '15 at 10:29

score 2 · Answer 1 · edited May 23 '17 at 10:24

2

There's an answer to your question here: https://stackoverflow.com/a/10337225/5111146

The solution is too move the try catch into the method called on timeout.

edited May 23 '17 at 10:24

Community

1
1

answered Jul 28 '15 at 10:29

James Brierley

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I can't do that in my case. – Stan Wiechers Jul 28 '15 at 10:31
Exactly what I thought. I'm not sure that throwing an error inside an anonymous function inside a timeout inside a try/catch would work. – evolutionxbox Jul 28 '15 at 10:31
I understand the issue. I just can't have the node.js process to terminate. – Stan Wiechers Jul 28 '15 at 10:33
Why can't you use something like: require('vm').runInNewContext("setTimeout(function(){try { undefinedMethod(); } catch(error) { console.log(error); } },100)",ctx) – James Brierley Jul 28 '15 at 10:36
Because this doesn't help if there other embedded closures. I like to have a safety belt as last measure, but it looks its not a possibility. – Stan Wiechers Jul 28 '15 at 10:48
I'm not familiar with node.js. Does it have the onError event? (http://stackoverflow.com/a/951811/5111146) – James Brierley Jul 28 '15 at 10:50

score 0 · Answer 2 · answered Nov 17 '20 at 08:36

If the error is going to be consistent and can be handled in the code outside the vm context, global handler for unhandled exception and rejection can be used catch these errors.

process.on('unhandledRejection', console.log);
process.on('uncaughtException',  console.log);

Throwing an Error inside the context of a closure is not reaching the catch clause

2 Answers2