Fastify: The Fast and Low Overhead Node.js Web Framework

Fastify is a highly efficient web framework for Node.js, designed to deliver maximum performance by minimizing overhead. Whether you are building an API gateway, a microservice, or a full-fledged server-side application, Fastify offers a plethora of features to streamline development while ensuring scalability and reliability.

Getting Started with Fastify

To begin, you need to install Fastify using npm or yarn:

 npm install fastify --save 

or

 yarn add fastify 

Basic Fastify Server

Here’s a basic Fastify server setup:

 const fastify = require('fastify')({ logger: true });
fastify.get('/', async (request, reply) => {
  return { message: 'Hello Fastify!' };
});
const start = async () => {
  try {
    await fastify.listen(3000);
  } catch (err) {
    fastify.log.error(err);
    process.exit(1);
  }
};
start(); 

Route Parameters and Queries

Fastify allows you to handle route parameters and query strings with ease:

 fastify.get('/user/:id', async (request, reply) => {
  const { id } = request.params;
  const { name } = request.query;
  return { id, name };
}); 

Handling POST Requests

Handling POST requests with Fastify is straightforward:

 fastify.post('/user', async (request, reply) => {
  const { username, email } = request.body;
  return { username, email };
}); 

Schema Validation

Fastify embraces JSON Schema for payload validation:

 const userSchema = {
  type: 'object',
  required: ['username', 'email'],
  properties: {
    username: { type: 'string' },
    email: { type: 'string' }
  }
};
fastify.post('/signup', { schema: { body: userSchema } }, async (request, reply) => {
  const { username, email } = request.body;
  return { status: 'success', username, email };
}); 

Request Lifecycle Hooks

Fastify provides several hooks to handle different stages of the request lifecycle:

 fastify.addHook('preHandler', async (request, reply) => {
  request.log.info('A request is being processed');
});
fastify.addHook('onSend', async (request, reply, payload) => {
  reply.header('Custom-Header', 'FastifyDemo');
  return payload;
}); 

Plugins in Fastify

Plugins are a core feature of Fastify, enabling code reusability and separation of concerns:

 fastify.register(require('fastify-auth'));
fastify.addHook('preHandler', fastify.auth([
  async (request, reply) => {
    const apiKey = request.headers['api-key'];
    if (!apiKey || apiKey !== 'secret') {
      reply.code(401).send({ error: 'Unauthorized' });
    }
  }
])); 

Example Application

Here’s a more comprehensive example combining several Fastify features:

 const fastify = require('fastify')({ logger: true });
fastify.register(require('fastify-auth'));
const userSchema = {
  type: 'object',
  required: ['username', 'email'],
  properties: {
    username: { type: 'string' },
    email: { type: 'string' }
  }
};
fastify.addHook('preHandler', fastify.auth([
  async (request, reply) => {
    const apiKey = request.headers['api-key'];
    if (!apiKey || apiKey !== 'valid-key') {
      reply.code(401).send({ error: 'Unauthorized' });
    }
  }
]));
fastify.post('/signup', { schema: { body: userSchema } }, async (request, reply) => {
  const { username, email } = request.body;
  return { status: 'success', username, email };
});
fastify.get('/user/:id', async (request, reply) => {
  const { id } = request.params;
  return { id, username: 'John Doe', email: 'john.doe@example.com' };
});
const start = async () => {
  try {
    await fastify.listen(3000);
  } catch (err) {
    fastify.log.error(err);
    process.exit(1);
  }
};
start(); 

With these features, Fastify becomes an indispensable tool for building high-performance Node.js applications.

Feel free to explore more about Fastify here.

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