In a plug-in I am using NPN_Evaluate() to execute some Javascript. How can I detect wether the Javascript raises an exception? Basically I want to execute any piece of Javascript and get the result from it or detect if it raised an exception.

I tried wrapping my Javascript code like this:

try {
  // Injected Javascript code here
}
catch (exc) {
  exc;
}

That way the result from NPN_Evaluate() will be an NPObject* containing a property "message" with the exception message if something goes wrong. But how can I know that it is an exception? It might as well be a result from the injected Javascript code.

Am I approaching this the wrong way? Can I detect an exception without catching it in Javascript and returning the exception as the result?