Tutorial: Build a Real-time Chat Application

What We’ll Build

In this tutorial, we’ll build a real-time chat application with:

User authentication (JWT)
Real-time messages via Socket.io
User management
Message history with pagination
Type-safe TypeScript throughout

This tutorial covers core Feathers concepts by building a real application. We’ll use actual code from the Feathers framework source.

Prerequisites

Node.js 20 or later
Basic TypeScript/JavaScript knowledge
Familiarity with async/await

Project Setup

Initialize the project

Create a new Feathers application:

npm create feathers chat-app
cd chat-app

When prompted:

Choose TypeScript
Select Express as the HTTP framework
Choose Memory for the database (for simplicity)
Select Local Authentication (username/password)

Install dependencies

The CLI installs dependencies automatically, but you can also install them manually:

npm install @feathersjs/feathers @feathersjs/express @feathersjs/socketio \
            @feathersjs/authentication @feathersjs/authentication-local \
            @feathersjs/memory @feathersjs/schema @feathersjs/typebox

Project structure

Your project structure should look like:

chat-app/
├── src/
│   ├── services/
│   │   ├── messages/
│   │   └── users/
│   ├── app.ts
│   └── index.ts
├── package.json
└── tsconfig.json

Building the Application

1. Create the Feathers App

Let’s start by creating the main application instance:

src/app.ts

import { feathers } from '@feathersjs/feathers'
import express, {
  rest,
  json,
  urlencoded,
  cors,
  compression,
  errorHandler,
  notFound
} from '@feathersjs/express'
import socketio from '@feathersjs/socketio'

// Create the Feathers app
const app = express(feathers())

// Configure middleware
app.use(cors())
app.use(compression())
app.use(json())
app.use(urlencoded({ extended: true }))

// Configure transports
app.configure(rest())
app.configure(socketio())

export { app }

This creates an Express-compatible Feathers application, just like in the source:

packages/express/src/index.ts

export default function feathersExpress<S = any, C = any>(
  feathersApp?: FeathersApplication<S, C>,
  expressApp: Express = express()
): Application<S, C> {
  if (!feathersApp) {
    return expressApp as any
  }

  if (typeof feathersApp.setup !== 'function') {
    throw new Error('@feathersjs/express requires a valid Feathers application instance')
  }

  const app = expressApp as any as Application<S, C>
  // ... merges Feathers and Express functionality

  return app
}

2. Create the Users Service

Users need to authenticate, so let’s create a users service:

src/services/users/users.schema.ts

import { Type } from '@feathersjs/typebox'
import type { Static } from '@feathersjs/typebox'

// Define the user schema
export const userSchema = Type.Object(
  {
    id: Type.Number(),
    email: Type.String({ format: 'email' }),
    password: Type.String(),
    createdAt: Type.Number(),
    updatedAt: Type.Number()
  },
  { $id: 'User', additionalProperties: false }
)

export type User = Static<typeof userSchema>

// Data for creating a user (no id yet)
export const userDataSchema = Type.Pick(userSchema, ['email', 'password'])
export type UserData = Static<typeof userDataSchema>

// User data that's safe to return to clients (no password)
export const userExternalSchema = Type.Omit(userSchema, ['password'])
export type UserExternal = Static<typeof userExternalSchema>

src/services/users/users.service.ts

import { memory } from '@feathersjs/memory'
import type { Application } from '../../declarations'

export const userPath = 'users'

export const userMethods = ['find', 'get', 'create', 'patch', 'remove'] as const

export class UserService extends memory({
  id: 'id',
  startId: 1,
  paginate: {
    default: 10,
    max: 50
  }
}) {}

export const users = (app: Application) => {
  // Register the service
  app.use(userPath, new UserService(), {
    methods: userMethods
  })

  // Add hooks
  app.service(userPath).hooks({
    before: {
      create: [
        async (context) => {
          // Add timestamps
          context.data.createdAt = Date.now()
          context.data.updatedAt = Date.now()
        }
      ],
      patch: [
        async (context) => {
          // Update timestamp
          context.data.updatedAt = Date.now()
        }
      ]
    },
    after: {
      all: [
        async (context) => {
          // Remove password from responses
          if (context.result) {
            if (Array.isArray(context.result)) {
              context.result = context.result.map(user => {
                const { password, ...rest } = user
                return rest
              })
            } else if (context.result.data) {
              // Paginated result
              context.result.data = context.result.data.map(user => {
                const { password, ...rest } = user
                return rest
              })
            } else {
              const { password, ...rest } = context.result
              context.result = rest
            }
          }
        }
      ]
    }
  })
}

The memory adapter implements all CRUD methods:

packages/memory/src/index.ts

export class MemoryService<
  Result = any,
  Data = Partial<Result>,
  ServiceParams extends AdapterParams = AdapterParams,
  PatchData = Partial<Data>
> extends MemoryAdapter<Result, Data, ServiceParams, PatchData> {
  async find(params?: ServiceParams): Promise<Paginated<Result> | Result[]> {
    return this._find({
      ...params,
      query: await this.sanitizeQuery(params)
    })
  }

  async get(id: Id, params?: ServiceParams): Promise<Result> {
    return this._get(id, {
      ...params,
      query: await this.sanitizeQuery(params)
    })
  }

  async create(data: Data | Data[], params?: ServiceParams): Promise<Result | Result[]> {
    if (Array.isArray(data) && !this.allowsMulti('create', params)) {
      throw new MethodNotAllowed('Can not create multiple entries')
    }
    return this._create(data, params)
  }
}

3. Create the Messages Service

Now let’s create the messages service:

src/services/messages/messages.schema.ts

import { Type } from '@feathersjs/typebox'
import type { Static } from '@feathersjs/typebox'

export const messageSchema = Type.Object(
  {
    id: Type.Number(),
    text: Type.String(),
    userId: Type.Number(),
    createdAt: Type.Number(),
    updatedAt: Type.Number()
  },
  { $id: 'Message', additionalProperties: false }
)

export type Message = Static<typeof messageSchema>

export const messageDataSchema = Type.Pick(messageSchema, ['text', 'userId'])
export type MessageData = Static<typeof messageDataSchema>

src/services/messages/messages.service.ts

import { memory } from '@feathersjs/memory'
import type { Application } from '../../declarations'

export const messagePath = 'messages'

export const messageMethods = ['find', 'get', 'create', 'patch', 'remove'] as const

export class MessageService extends memory({
  id: 'id',
  startId: 1,
  paginate: {
    default: 25,
    max: 100
  }
}) {}

export const messages = (app: Application) => {
  // Register the service
  app.use(messagePath, new MessageService(), {
    methods: messageMethods
  })

  // Add hooks
  app.service(messagePath).hooks({
    before: {
      create: [
        async (context) => {
          // Add timestamp
          context.data.createdAt = Date.now()
          context.data.updatedAt = Date.now()

          // Set user ID from authenticated user
          if (context.params.user) {
            context.data.userId = context.params.user.id
          }
        }
      ],
      all: [
        async (context) => {
          // Log all method calls
          console.log(`${context.method} on ${context.path}`)
        }
      ]
    },
    after: {
      create: [
        async (context) => {
          // Populate user information
          const user = await app.service('users').get(context.result.userId)
          context.result.user = user
        }
      ]
    }
  })

  // Publish events to authenticated users only
  app.service(messagePath).publish('created', (data, context) => {
    return app.channel('authenticated')
  })
}

4. Set Up Authentication

Add JWT authentication:

src/authentication.ts

import { AuthenticationService } from '@feathersjs/authentication'
import { LocalStrategy } from '@feathersjs/authentication-local'
import { JWTStrategy } from '@feathersjs/authentication'
import type { Application } from './declarations'

export const authentication = (app: Application) => {
  const authService = new AuthenticationService(app)

  // Register strategies
  authService.register('jwt', new JWTStrategy())
  authService.register('local', new LocalStrategy())

  // Register the service
  app.use('authentication', authService)
}

The authentication service from the source:

packages/authentication/src/service.ts

export class AuthenticationService
  extends AuthenticationBase
  implements Partial<ServiceMethods<AuthenticationResult, AuthenticationRequest>>
{
  constructor(app: any, configKey = 'authentication', options = {}) {
    super(app, configKey, options)

    hooks(this, {
      create: [resolveDispatch(), event('login'), connection('login')],
      remove: [resolveDispatch(), event('logout'), connection('logout')]
    })

    this.app.on('disconnect', async (connection: RealTimeConnection) => {
      await this.handleConnection('disconnect', connection)
    })
  }

  async create(data: AuthenticationRequest, params?: AuthenticationParams) {
    const authStrategies = params.authStrategies || this.configuration.authStrategies

    const authResult = await this.authenticate(data, params, ...authStrategies)

    if (authResult.accessToken) {
      return authResult
    }

    const [payload, jwtOptions] = await Promise.all([
      this.getPayload(authResult, params),
      this.getTokenOptions(authResult, params)
    ])

    const accessToken = await this.createAccessToken(payload, jwtOptions, params.secret)

    return {
      accessToken,
      ...authResult
    }
  }
}

5. Wire Everything Together

Update your main app file:

src/app.ts

import { feathers } from '@feathersjs/feathers'
import express, {
  rest,
  json,
  urlencoded,
  cors,
  compression,
  errorHandler,
  notFound
} from '@feathersjs/express'
import socketio from '@feathersjs/socketio'
import { authentication } from './authentication'
import { users } from './services/users/users.service'
import { messages } from './services/messages/messages.service'

// Create the Feathers app
const app = express(feathers())

// Configure middleware
app.use(cors())
app.use(compression())
app.use(json())
app.use(urlencoded({ extended: true }))

// Configure transports
app.configure(rest())
app.configure(socketio({
  cors: {
    origin: '*'
  }
}))

// Configure authentication
app.set('authentication', {
  secret: 'your-secret-key',
  authStrategies: ['jwt', 'local'],
  jwtOptions: {
    header: { typ: 'access' },
    audience: 'https://yourdomain.com',
    issuer: 'feathers',
    algorithm: 'HS256',
    expiresIn: '1d'
  },
  local: {
    usernameField: 'email',
    passwordField: 'password'
  },
  entity: 'user',
  service: 'users',
  entityId: 'id'
})

app.configure(authentication)

// Configure services
app.configure(users)
app.configure(messages)

// Error handling
app.use(notFound())
app.use(errorHandler())

export { app }

src/index.ts

import { app } from './app'

const port = 3030

app.listen(port).then(() => {
  console.log(`Feathers app listening on http://localhost:${port}`)
})

6. Test the Application

Start your server:

npm run dev

Test the API:

curl -X POST http://localhost:3030/users \
  -H "Content-Type: application/json" \
  -d '{
    "email": "[email protected]",
    "password": "password123"
  }'

Real-time Client

Create a simple HTML client to test real-time features:

public/index.html

<!DOCTYPE html>
<html>
<head>
  <title>Feathers Chat</title>
  <script src="//unpkg.com/@feathersjs/client@^5.0.0/dist/feathers.js"></script>
  <script src="//unpkg.com/socket.io-client@^4.0.0/dist/socket.io.min.js"></script>
</head>
<body>
  <div id="app">
    <h1>Feathers Chat</h1>
    <div id="login">
      <input id="email" type="email" placeholder="Email">
      <input id="password" type="password" placeholder="Password">
      <button onclick="login()">Login</button>
      <button onclick="signup()">Sign Up</button>
    </div>
    <div id="chat" style="display: none;">
      <div id="messages"></div>
      <input id="message-text" placeholder="Type a message">
      <button onclick="sendMessage()">Send</button>
    </div>
  </div>

  <script>
    const socket = io('http://localhost:3030')
    const app = feathers()

    app.configure(feathers.socketio(socket))
    app.configure(feathers.authentication())

    const messagesDiv = document.getElementById('messages')

    // Listen for new messages
    app.service('messages').on('created', (message) => {
      addMessage(message)
    })

    async function signup() {
      const email = document.getElementById('email').value
      const password = document.getElementById('password').value

      try {
        await app.service('users').create({ email, password })
        await login()
      } catch (error) {
        console.error('Signup error:', error)
      }
    }

    async function login() {
      const email = document.getElementById('email').value
      const password = document.getElementById('password').value

      try {
        await app.authenticate({
          strategy: 'local',
          email,
          password
        })

        document.getElementById('login').style.display = 'none'
        document.getElementById('chat').style.display = 'block'

        // Load existing messages
        const result = await app.service('messages').find({
          query: { $sort: { createdAt: -1 }, $limit: 25 }
        })

        result.data.reverse().forEach(addMessage)
      } catch (error) {
        console.error('Login error:', error)
      }
    }

    async function sendMessage() {
      const text = document.getElementById('message-text').value

      if (text.trim()) {
        await app.service('messages').create({ text })
        document.getElementById('message-text').value = ''
      }
    }

    function addMessage(message) {
      const div = document.createElement('div')
      div.textContent = `${message.user?.email || 'Unknown'}: ${message.text}`
      messagesDiv.appendChild(div)
    }
  </script>
</body>
</html>

Advanced Features

Custom Hooks

Create reusable hooks for common tasks:

src/hooks/log.ts

import { HookContext } from '@feathersjs/feathers'

export const logRuntime = () => async (context: HookContext, next: () => Promise<void>) => {
  const start = Date.now()
  await next()
  const duration = Date.now() - start
  console.log(`${context.method} on ${context.path} took ${duration}ms`)
}

// Use it
app.service('messages').hooks({
  around: {
    all: [logRuntime()]
  }
})

Schema Validation

Use TypeBox schemas for validation:

src/services/messages/messages.hooks.ts

import { resolve, validateData } from '@feathersjs/schema'
import { messageDataSchema } from './messages.schema'

export const messageDataResolver = resolve<Message, HookContext>({
  properties: {
    userId: async (_value, _message, context) => {
      return context.params.user?.id
    },
    createdAt: async () => Date.now(),
    updatedAt: async () => Date.now()
  }
})

app.service('messages').hooks({
  before: {
    create: [
      validateData(messageDataSchema),
      messageDataResolver
    ]
  }
})

What You’ve Learned

Services

Services are the core abstraction in Feathers. They handle data operations and automatically expose REST and real-time APIs.

Hooks

Hooks are middleware that run before, after, or around service methods. They’re perfect for validation, authorization, and data transformation.

Authentication

Feathers provides a flexible authentication system with JWT tokens and multiple strategies.

Real-time

Socket.io integration gives you real-time capabilities out of the box. Events are automatically sent when data changes.

Next Steps

Add a Database

Replace the memory adapter with MongoDB or PostgreSQL

File Uploads

Handle file uploads with multipart/form-data

Email Verification

Add email verification for new users

Deploy

Deploy your app to production

The complete source code for this tutorial is available in the Feathers repository. Check out the test files for more examples!

Getting Started

Core Concepts

Guides

Tutorial: Build a Real-time Chat Application

What We’ll Build

Prerequisites

Project Setup

Building the Application

1. Create the Feathers App

2. Create the Users Service

3. Create the Messages Service

4. Set Up Authentication

5. Wire Everything Together

6. Test the Application

Real-time Client

Advanced Features

Custom Hooks

Schema Validation

What You’ve Learned

Next Steps

Add a Database

File Uploads

Email Verification

Deploy

Build docs developers (and LLMs) love

Getting Started

Core Concepts

Guides

​What We’ll Build

​Prerequisites

​Project Setup

​Building the Application

​1. Create the Feathers App

​2. Create the Users Service

​3. Create the Messages Service

​4. Set Up Authentication

​5. Wire Everything Together

​6. Test the Application

​Real-time Client

​Advanced Features

​Custom Hooks

​Schema Validation

​What You’ve Learned

​Next Steps

Add a Database

File Uploads

Email Verification

Deploy

Build docs developers (and LLMs) love

What We’ll Build

Prerequisites

Project Setup

Building the Application

1. Create the Feathers App

2. Create the Users Service

3. Create the Messages Service

4. Set Up Authentication

5. Wire Everything Together

6. Test the Application

Real-time Client

Advanced Features

Custom Hooks

Schema Validation

What You’ve Learned

Next Steps