Best way to Handle Exception Globally in Node.js with Express 4?

Question

AS We have Exception filter in asp.net MVC, do we have similar kind of functionality in node.js with express 4 also?

I have tried following articles but didn't find the desired solution.

http://www.nodewiz.biz/nodejs-error-handling-pattern/

I have also tried below on app.js

process.on('uncaughtException', function (err) {
  console.log(err);
})

ref article: http://shapeshed.com/uncaught-exceptions-in-node/

Any help would be appreciable.

Answer 1

Errors might came from and caught in various locations thus it's recommended to handle errors in a centralized object that handles all types of errors. For example, error might occurs in the following places:

1.Express middleware in case of SYNC error in a web request

app.use(function (err, req, res, next) {
//call handler here
});

2.CRON jobs (scheduled tasks)

3.Your initialization script

4.Testing code

5.Uncaught error from somewhere

    process.on('uncaughtException', function(error) {
 errorManagement.handler.handleError(error);
 if(!errorManagement.handler.isTrustedError(error))
 process.exit(1)
});

6.Unhandled promise rejection

 process.on('unhandledRejection', function(reason, p){
   //call handler here
});

---

Then when you catch errors, pass them to a centralized error handler:

    module.exports.handler = new errorHandler();

function errorHandler(){
    this.handleError = function (error) {
        return logger.logError(err).then(sendMailToAdminIfCritical).then(saveInOpsQueueIfCritical).then(determineIfOperationalError);
    }

---

For more information read bullet 4' here (+ other best practices and more than 35 quotes and code examples)

Answer 2

In express, it's standard practice to have a catch all error handler attached. A barebones error handler would look like

// Handle errors
app.use((err, req, res, next) => {
    if (! err) {
        return next();
    }

    res.status(500);
    res.send('500: Internal server error');
});

Along with this, you will need to catch errors anywhere they can happen and pass them as a param in next(). This will make sure that the catch all handler catches the errors.