Fastify basics tutorial | A better alternative to Express

In this blog, we will learn everything you need to know to get started with Fastify.

Video tutorial

What is Fastify?

Fastify is a web framework for Node.js. It is a lightweight, fast, and flexible framework for building modern server-side web applications.

It is pretty similar to Express. But it has some features that make it standout from the others.

• Schema Validation
• Plugin System

Setup

npm init -y
npm i fastify

Create a basic node server

const fastify = require('fastify')
const app = fastify({ logger: true })
const PORT = process.env.PORT || 8000
app.listen(PORT).catch(error => {
    app.log.error(error)
    process.exit()
})

Explanation:

• app is the instance of Fastify. Fastify has a separate login system. We are enabling the logger by passing the object.
• PORT is the port number.
• app.listen is the function that starts the server. If any error occurs, it will log the error and exit the process.

Start the server

node <file>

Or, you can use nodemon to restart the server whenever you make a change.

npm i -g nodemon
nodemon <file>

You can see it is pretty similar to Express. Let’s create some simple api.

I will use the following data.

[
    {
        "id": 1,
        "name": "Innis Gladeche",
        "email": "igladeche0@yellowbook.com",
        "gender": "Male",
        "country": "North Korea"
    },
    {
        "id": 2,
        "name": "Woodman Haylands",
        "email": "whaylands1@addtoany.com",
        "gender": "Male",
        "country": "Russia"
    },
    {
        "id": 3,
        "name": "Caleb Galbraith",
        "email": "cgalbraith2@last.fm",
        "gender": "Male",
        "country": "Brazil"
    },
    {
        "id": 4,
        "name": "Earlie Beddie",
        "email": "ebeddie3@nsw.gov.au",
        "gender": "Genderqueer",
        "country": "Ukraine"
    },
    {
        "id": 5,
        "name": "Marcellus Cloake",
        "email": "mcloake4@opensource.org",
        "gender": "Male",
        "country": "Sweden"
    },
    {
        "id": 6,
        "name": "Mada Poll",
        "email": "mpoll5@washington.edu",
        "gender": "Female",
        "country": "Sweden"
    },
    {
        "id": 7,
        "name": "Ashly Goodrum",
        "email": "agoodrum6@photobucket.com",
        "gender": "Female",
        "country": "United States"
    },
    {
        "id": 8,
        "name": "Obed Mabbs",
        "email": "omabbs7@lycos.com",
        "gender": "Male",
        "country": "China"
    },
    {
        "id": 9,
        "name": "Margalo Weild",
        "email": "mweild8@freewebs.com",
        "gender": "Female",
        "country": "Sweden"
    },
    {
        "id": 10,
        "name": "Seth Jex",
        "email": "sjex9@deliciousdays.com",
        "gender": "Male",
        "country": "France"
    }
]

GET route

const getUsers = (request, reply) => users
app.get('/getUsers' getUsers)

• To handle a request use the HTTP method from app. Useapp.get for GET requests andapp.post for POST requests and so on.
• The function takes two arguments. api endpoint and callback function.
• The handler function takes two arguments. request and reply.
• To return a response, just return data from the function. We are returning the users array.

Query parameter

You can send additional information with the URL as query parameters.

Example:

http://localhost:8000/getUsers?gender=female

After the question mark, we have key-value pairs. This is what we call query parameters. Let’s use that in our /getUsers route. We will get users of specific gender with a query parameter.

const getUsers = (request, reply) => {
    const { gender } = request.query
    if (!gender) return users
    const filteredUsers = users.filter(
        (user) => user.gender.toLowerCase() === gender.toLowerCase()
    )
    return filteredUsers
}
app.get('/getUsers' getUsers)

Explanation:

• We are getting gender from the request.query object.
• If gender doesn’t exist, we will send users.
• Else we will filter users based on gender and return that as the response.

Post Route

Let’s create a new user.

const addUser = request => {
    const id = users.length + 1
    const newUser = { ...request.body, id }
    users.push(newUser)
    return newUser
}
app.post('/addUser', addUser)

Explanation:

• This time we will use app.post instead of app.get.
• We are getting the request body from the request object.
• Then we are creating a new user with the information of the request body and adding it to the users array.

Schema validation

A schema is a structural representation of some kind of data. In a schema, you can specify what preterites the data will have and what values will be stored.
Fastify has a built-in schema validation. You can have schema validation for request body, query parameters, response, and headers.
It is my favorite feature of Fastify. Let’s use that in our /addUser route.

const addUserOptions = {
    schema: {
        body: {
            type: 'object',
            properties: {
                name: {
                    type: 'string',
                },
                age: {
                    type: ['number', 'string'],
                },
                gender: {
                    type: 'string',
                    enum: ['male', 'female', 'others'],
                },
            },
            required: ['name', 'gender'],
        },
    },
}
const addUser = request => {
    const id = users.length + 1
    const newUser = { ...request.body, id }
    users.push(newUser)
    return newUser
}
app.post('/addUser', addUserOptions, addUser)

Explanation:

• We are padding options object as 2nd argument.
• We are creating a schema for the request body.
• Include the necessary properties inside the properties object and their type.
• Include the required properties inside the required array.
• To learn more about schema validation please check the video tutorial.

So that’s all I wanted to teach you. To learn more about Fastify please check the video tutorial.
I have tried to explain things simply. If you get stuck, you can ask me questions.

By the way, I am looking for a new opportunity in a company where I can provide great value with my skills. If you are a recruiter, looking for someone skilled in full stack web development and passionate about revolutionizing the world, feel free to contact me. Also, I am open to talking about any freelance project.

See my work from here