Javascript Custom Exception

Question

I have tried for a couple of days researching on how to create a custom exception in a try/catch.

Here is what I am attempting to do:

I have an included JS file in my html page. The JS file defines a custom object, as well as defining methods for the object.

Next, in the html page I am doing the following:

try {
   MyObj = new CustomObj;     //from the included JS file.
   MyObj.CustomMethod();      //also from the included JS file.
} catch(e) {
   alert("Error in either the create of the object, or the method. Error is " + e.description)
}

I need to be able, within the code for the CustomMethod(), to set the Error Object's properties that are captured in the catch statement. For example:

  CustomMethod = function{
     try{
       document.getelementById("field1").value = "my value";
     } catch(err) {
       //Set the return error
       ReturnErr.description = "There was an error!";
     }
  };

Can this be done? From what I have tried, I have used the throw statement, but it does not effect the Error Object, thus the catch section is never triggered. In face, the custom message is only shown in the Console.

Thanks ahead of time.

Possible duplicate of How do I create a custom Error in JavaScript? — Matías Fidemraizer
– Matías Fidemraizer, Commented Dec 21, 2016 at 14:13

Maxim Shoustin · Accepted Answer · 2016-12-21 16:11:22Z

2

Try:

function MyException(_message, _data) {
    this.message = _message;
    this.data = _data;
    this.name = "MyException";
}

Usage

try{
      //...                   
   }
   catch(_error){
      throw new MyException(message, _error);
   }

Hope it will help you to sort things out

edited Dec 21, 2016 at 16:11

answered Dec 21, 2016 at 14:07

Maxim Shoustin

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3 Comments

ewm76903 Over a year ago

Thanks. But I guess that I cannot modify the (_error) in your example?

Maxim Shoustin Over a year ago

@EricMeans, sorry, typo, pass error as second parameter.

ewm76903 Over a year ago

Sorry, what I meant was not to have to use the throw in the catch block, but to set the error that the catch block gets, in the called function/method from the try block. Does that make any sense?

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