NodeJs — Creating a generic error handling

Hello guys!

Today we’re going to see how to create a global error handling in NodeJs with no need to implement many try/catch blocks to your code.

Access the example code on Github

We recomend you to also take a look into this YouTube video

Steps

To start we will create the entire initial structure of a project for a better understanding.

REQUIREMENTS:

• Nodejs
• Npm
• Express

1. Add a new folder to your computer and name it “generic-error-handler”
2. Access the new folder, open your terminal and type:

npm init -y
yarn init -y

3. Then we will add some packages to our project

npm i express
yarn add express

4. Open the package.json file and add the following command to the “scripts” session:

"dev": "node app.js"

5. Add the file app.js to your project and type the following code, this will be our initial configuration

const express = require('express')
const app = express()

// enabling our app to work with JSON
app.use(express.json());

// adding a default route to our application
app.get('/', (req, res, next) => {
    res.send({
        message: 'Hello world'
    })
})

app.listen(3001, () => {
    console.log('App listening at 3001')
})

With this you’ll be able to see the result below

6. Add a file called “example.controller.js”, then copy and paste the code below

class ExampleController { 
    static throwErrorMethod(req, res) {
        throw new Error('Some error that can happen during the app execution');
    }
}

module.exports = ExampleController;

7. Back to the app.js, we will add the code responsible for “wrap” our routes, and handle the errors

// this will be our wrapper
const use = fn => (req, res, next) => Promise.resolve(fn(req, res, next)).catch(next);

// this is the route we're going to "wrap"
app.get('/example', use(exampleController.throwErrorMethod));

// this will be our middleware, our ErrorHandler
app.use(function(err, req, res, next) {
    res.status(500).send({
        message: err.message
    })
});

8. Finally run your code. =)

npm run dev 
yarn dev

You can test your routes using postman app: