How can you deal with error handling in Express.js? Explain with an example.

Express.js - Interview Questions

Error handling is much easier in the Express versions over Express 4.0. Use the following steps to do the error handling:

Create an Express.js application. There is no built-in middleware like error handler in express 4.0, so you have to either install a middleware or create a custom one.

Create a Middleware :

Create a middleware as following:

// error handler  
app.use(function(err, req, res, next) {  
// set locals, only providing error in development  
res.locals.message = err.message;  
res.locals.error = req.app.get('env') === 'development' ? err : {};  
// render the error page  
res.status(err.status || 500);  
res.render('error');  
}); â€‹

Install Error Handler Middleware :

Install the errorhandler as following :

npm install errorhandler --save

Create a variable :

var errorhandler = require('errorhandler')

Use the middleware as following :

if (process.env.NODE_ENV === 'development') {  
 // only use in development  
  app.use(errorhandler({log: errorNotification}))  
}  
function errorNotification(err, str, req) {  
 var title = 'Error in ' + req.method + ' ' + req.url  
 notifier.notify({  
   title: title,  
   message: str  
 })  
}