Nodejs throw exception

Question

I'm working on Nodejs service-side application, my case is that i want to return the throw an exception to the caller(who did call the function), i did two cases, one outside the callback, and the another inside the callback, also the parent has try catch blocks.

concept : throw(Business function)-->throw (Business function) -->try & catch

Outside the callback is working correctly. Inside the callback didn't return the exception to the parent.

I want to to this scenario,because I'm looking to throw an exception to the parent and stop completion the functions, and this's exist in Java, C++, C and .NET.

So why this scenario is not working with me ?!

My example here with 2 different cases :

FactoryController.prototype.create = function (callback) {
    //The throw is working, and the exception is returned.
    throw new Error('An error occurred'); //outside callback 
    try {
        this.check(function (check_result) {
            callback(check_result);
        });
    } catch (ex) {
        throw new Error(ex.toString());
    }
}

FactoryController.prototype.create = function (callback) {
    try {
        this.check(function (check_result) {
            //The throw is not working on this case to return the exception to the caller(parent)
            throw new Error('An error occurred'); //inside callback 
        });
    } catch (ex) {
        throw new Error(ex.toString());
    }
}

J.G.Sebring · Accepted Answer · 2015-12-01 10:31:11Z

14

Exceptions occurs because you are throwing the errors. If you rather want to return the error to the caller, you need to provide it in the callback. Add the error as parameter to the callback.

Usually the callback pattern is callback(error, result);

callback(new Error(ex.toString())); // ignore result param

Error handling in Nodejs

answered Dec 1, 2015 at 10:31

J.G.Sebring

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3 Comments

Muhamet Aljobairi Over a year ago

Already I'm working on this scenario, but there any more solutions ?!? in this case , you need to check if the err has been happened or not through if statement

J.G.Sebring Over a year ago

In the callback, yes. It's nothing more advanced than myCallbackFunction(error, result) { if (error != null) { // handle error } ...

J.G.Sebring Over a year ago

No worries, feel free to upvote and accept answer if it helped you.

Chamath Nanayakkara · Accepted Answer · 2018-05-22 23:12:05Z

would the below code satisfy your requirement

'use strict';
var  inherits =require('util').inherits;
//Parent
function factoryController(n){
     this.name=n;
 }
 //parent prototype function
 factoryController.prototype.create = function (type) {
     var retVal="";
     try {
     throw new Error('An error occurred'); 
      retVal=this.name+' is a '+ type;
     }
     catch(e){
         retVal=e.toString();
     }
     return retVal;

}
 function subsidaryController(name) {
       // Call parent constructor 
        factoryController.call(this, name);

    }
inherits(subsidaryController,factoryController);
// Additional member functions 
 subsidaryController.prototype.fn = function (locations) {
     var retVal="";
     try {
          throw new Error('Another error occurred'); 
          retVal='Having branches in' + locations;
     }
     catch(e){
         retVal=e.toString();
     }
     return retVal;
 }   
 let fc = new subsidaryController('ABC Factory');
console.log(fc.create('Manufacturer' ));
console.log(fc.fn('Europe and Asia'));

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