section3.10.md

Section 3.10: Error handling in Express

In Express, you can define unified error handler for handling errors occurred in application. Define then handler at the end of all routes and logic code.

// Example
let express = require('express');
let app = express();

// GET /names/Morol
app.get('/names/:name', function(req, res, next){
  if (req.params.name == 'Morol'){
    return res.send('Valid Name');
  } else{
    //pass to error handler
    next(new Error('Not valid name'));
  }
});


//error handler
app.use(function(err, req, res, next){
  console.log(err.stack); // e.g., Not valid name
  return res.status(500).send('Internal Server Occurred');
});

app.listen(3000);

• http://localhost:3000/names/Morol
  • Valid Name
• http://localhost:3000/names/Jinnatul
  • Not valid name
  • Internal Server Occurred (500 status code)