In this tutorial, you'll learn how to build a chat app with React, complete with typing indicators, online status, and more.
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README.md

Build a Slack Clone with React and Pusher Chatkit

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In this tutorial, you’ll learn how to build a chat app with React and Chatkit.

When we're done, we'll have a chat application complete with typing indicators, a "who's online" list, and message history:

If you think this sounds like a lot to tackle in one tutorial, you'd normally be right!

However, because we'll be using Chatkit, we can more or less focus exclusively on the front-end React code while Chatkit does the heavy lifting.

What is Chatkit?

Chatkit is a hosted API that helps you build impressive chat features into your applications with less code. Features like,

  • Group chat
  • One-to-one chat
  • Private chat
  • Typing indicators
  • "Who's online" presence
  • Read receipts
  • Photo, video, and audio messages

Using our cross-platform SDKs, all chat data is sent to our hosted API where we manage chat state and broadcast it to your clients:

You'll never have to worry about scale or infrastructure, we take care of it all for you.

Perhaps the best way to learn Chatkit is to start building, so I highly recommend you follow along. Along the way, you'll learn best practices when using Chatkit with React.

Steps

This tutorial has been written so that you can follow along, step by step. There are 12 steps in total.

Here's a quick rundown so you know what to expect:

  1. Download the React starter template
  2. Create your own Chatkit instance
  3. Setup a basic Node server
  4. Identifying the user
  5. Render the chat screen
  6. Connect to your Chatkit instance
  7. Create a Chatkit room
  8. Create a basic UI layout
  9. Subscribe to new messages
  10. Sending messages
  11. Add realtime typing indicators
  12. Add a "Who's online" list

Alright, let's code!

Step 1. Download the React starter template

Rather than start from absolute scratch, this walkthrough is based on a minimal starter template:

As you can see, the starter template doesn't contain any interesting logic - just boilerplate we need to run a React application and a simple Node server.

"Server? No one mentioned a server!"

If you're not too familiar with Node, don't worry 😊. After the next section, we won't need to touch the server.

To get started, download the starter template then run npm install:

git clone https://github.com/pusher/build-a-slack-clone-with-react-and-pusher-chatkit chatkit-tutorial
cd chatkit-tutorial
npm install

(Note: To see the completed code, you can view the completed branch or run git checkout complete locally.)

(Also note: This tutorial assumes the use of npm, but the equivalent yarn commands will work as well.)

Step 2. Create your own Chatkit instance

Now you've downloaded the starter template, let's create a Chatkit instance.

To create your own Chatkit instance, head to the dashboard and hit Create new:

Give your instance any name (I called mine "React Chat Tutorial") then take note of your Instance Locator and Secret Key in the Keys tab. We'll need them both in the next section.

Step 3. Setup a basic Node server

While most interactions will happen on the client, Chatkit also needs a server counterpart to create and manage users securely:

We won't authenticate users in this tutorial, but we'll still need to define a route that, when called, creates a Chatkit user.

Start by installing @pusher/chatkit-server:

npm install --save @pusher/chatkit-server

Then update ./server.js:

const express = require('express')
const bodyParser = require('body-parser')
const cors = require('cors')
+const Chatkit = require('@pusher/chatkit-server')

const app = express()

+const chatkit = new Chatkit.default({
+  instanceLocator: 'YOUR INSTANCE LOCATOR',
+  key: 'YOUR KEY',
+})

app.use(bodyParser.urlencoded({ extended: false }))
app.use(bodyParser.json())
app.use(cors())

+app.post('/users', (req, res) => {
+  const { username } = req.body
+  chatkit
+    .createUser({
+      id: username,
+      name: username
+    })
+    .then(() => res.sendStatus(201))
+    .catch(error => {
+      if (error.error_type === 'services/chatkit/user_already_exists') {
+        res.sendStatus(200)
+      } else {
+        res.status(error.status).json(error)
+      }
+    })
+})

+app.post('/authenticate', (req, res) => {
+  const authData = chatkit.authenticate({ userId: req.query.user_id })
+  res.status(authData.status).send(authData.body)
+})


const PORT = 3001
app.listen(PORT, err => {
  if (err) {
    console.error(err)
  } else {
    console.log(`Running on port ${PORT}`)
  }
})

Remember to replace "YOUR INSTANCE LOCATOR" and "YOUR KEY" with your own respective values.

There's a lot to unpack here, starting from the top:

  • First, we import Chatkit from @pusher/chatkit-server
  • Then, instantiate our own chatkit instance using the Instance Locator and Key we noted in the previous step
  • In the /users route, we take a username and create a Chatkit user through our chatkit instance
  • Authentication is the action of proving a user is who she says she is. When someone first connects to Chatkit, a request will be sent to /authenticate to authenticate them. The server needs to respond with a token (returned by chatkit.authenticate) if the request is valid. In our case, we'll - naïvely - assume that everyone is who they say they are, and return a token from chatkit.authenticate no matter what

Boom 💥! That's all we need to do on the server. Let's move on to the client...

Step 4. Identifying the user

When someone loads the app, we want to ask them who they are.

Once they hit Submit, we'll send their username to the server (to the /users route we just defined) and create a Chatkit user if one doesn't exist.

To collect the user's name, create a component called UsernameForm.js in in ./src/components/:

+import React, { Component } from 'react'

+class UsernameForm extends Component {
+ constructor(props) {
+   super(props)
+   this.state = {
+     username: '',
+   }
+   this.onSubmit = this.onSubmit.bind(this)
+   this.onChange = this.onChange.bind(this)
+ }

+ onSubmit(e) {
+   e.preventDefault()
+   this.props.onSubmit(this.state.username)
+ }

+ onChange(e) {
+    this.setState({ username: e.target.value })
+  }
+
+  render() {
+    return (
+      <div>
+        <div>
+          <h2>What is your username?</h2>
+          <form onSubmit={this.onSubmit}>
+            <input
+              type="text"
+              placeholder="Your full name"
+              onChange={this.onChange}
+            />
+            <input type="submit" />
+          </form>
+        </div>
+      </div>
+    )
+  }
+}
+
+ export default UsernameForm

Then update App.js:

import React, { Component } from 'react'
+import UsernameForm from './components/UsernameForm'

class App extends Component {
+  constructor() {
+    super()
+    this.state = {
+      currentUsername: '',
+    }
+    this.onUsernameSubmitted = this.onUsernameSubmitted.bind(this)
+  }

+  onUsernameSubmitted(username) {
+    fetch('http://localhost:3001/users', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+      },
+      body: JSON.stringify({ username }),
+    })
+      .then(response => {
+        this.setState({
+          currentUsername: username
+        })
+      })
+      .catch(error => console.error('error', error))
+  }

  render() {
-   return <h1>Chatly</h1>
+   return <UsernameForm onSubmit={this.onUsernameSubmitted} />
  }
}

export default App

Run the application using npm start and you'll see that the screen is rendered:

Starting from the top of App.js:

  • First, we import the UsernameForm component. It probably looks familiar to you because it uses a common React pattern called controlled components. You can read more about React forms here
  • In the render function we render the UsernameForm and hook up the onUsernameSubmitted event handler
  • When onUsernameSubmitted is called, we send a POST request to the /users route we just defined. If the request is successful, we update this.state.username so we can reference it later; otherwise, we console.error the error

Step 5. Render the chat screen

At the moment, we render the UsernameForm and it occupies the entire screen (see the above screenshot).

Once the username has been submitted, we'll want to transition to a different screen - namely, the chat screen.

To do that, we first need to create a ChatScreen.js component in ./src:

+import React, { Component } from 'react'
+
+class ChatScreen extends Component {
+  render() {
+    return (
+      <div>
+        <h1>Chat</h1>
+      </div>
+    )
+  }
+}
+
+export default ChatScreen

Then update App.js:

import React, { Component } from 'react'
import UsernameForm from './components/UsernameForm'
+import ChatScreen from './ChatScreen'

class App extends Component {
  constructor() {
    super()
    this.state = {
      currentUsername: '',
+     currentScreen: 'WhatIsYourUsernameScreen'
    }
    this.onUsernameSubmitted = this.onUsernameSubmitted.bind(this)
 }

  onUsernameSubmitted(username) {
    fetch('http://localhost:3001/users', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({ username }),
    })
      .then(response => {
        this.setState({
          currentUsername: username,
+         currentScreen: 'ChatScreen'
        })
      })
      .catch(error => console.error('error', error))
  }

 render() {
+    if (this.state.currentScreen === 'WhatIsYourUsernameScreen') {
      return <UsernameForm onSubmit={this.onUsernameSubmitted} />
+    }
+    if (this.state.currentScreen === 'ChatScreen') {
+      return <ChatScreen currentUsername={this.state.currentUsername} />
+    }
  }
}

export default App

Rather than use a router, we conditionally render the screen based on this.state.currentScreen.

Step 6. Connect to your Chatkit instance

Earlier, we installed @pusher/chatkit-server. Now we're in client-land, you'll need to install @pusher/chatkit-client as well:

npm install --save @pusher/chatkit-client

Then update ChatScreen.js:

import React, { Component } from 'react'
+import Chatkit from '@pusher/chatkit-client'

class ChatScreen extends Component {
+  constructor(props) {
+    super(props)
+    this.state = {
+      currentUser: {}
+    }
+  }

+  componentDidMount () {
+    const chatManager = new Chatkit.ChatManager({
+      instanceLocator: 'YOUR INSTANCE LOCATOR',
+      userId: this.props.currentUsername,
+      tokenProvider: new Chatkit.TokenProvider({
+        url: 'http://localhost:3001/authenticate',
+      }),
+    })
+
+    chatManager
+      .connect()
+      .then(currentUser => {
+        this.setState({ currentUser })
+     })
+     .catch(error => console.error('error', error))
+  }

  render() {
    return (
      <div>
        <h1>Chat</h1>
      </div>
    )
  }
}

export default ChatScreen

Remember to replace "YOUR INSTANCE LOCATOR" with yours that you noted earlier.

Again, starting from the top:

  • First, we import Chatkit
  • Then, instantiate our Chatkit ChatManager with our instanceLocator, userId (from this.props.currentUsername), and a custom TokenProvider. The TokenProvider points to the /authenticate route we defined earlier
  • Once ChatManager has been initialised, we can call connect. connect happens asynchronously and a Promise is returned. If you've followed these steps exactly, you will connect. That being said, watch out for any console.errors in case you missed something

Step 7. Create a Chatkit room

When using Chatkit, all messages are sent to a Chatkit room.

Rooms can be created programmatically (on the server or client using createRoom), or in the dashboard Inspector.

Creating rooms from the Inspector isn't really a good practice (it's mainly intended for testing) but for the purpose of this walkthrough, we'll do it anyway.

In the dashboard, head to the Console tab, where you'll find the Inspector and create a user with any name. I will call mine "Admin".

Then, create a room called "General":

It is really important to note the unique Room id highlighted above.

Step 8. Create a basic UI layout

This step marks a significant point in the walkthrough.

Now we have our boilerplate in place, we can rapidly start to build out chat features.

Going forward, we'll break down each feature into independent (reusable, if you want!) React components:

We will create each component as we go along, but to make the tutorial a bit easier to follow, let's set out the basic component UI layout now:

import React, { Component } from 'react'
import Chatkit from '@pusher/chatkit-client'

class ChatScreen extends Component {
  constructor(props) {
    super(props)
    this.state = {
      currentUser: {}
    }
  }

  componentDidMount () {
    const chatManager = new Chatkit.ChatManager({
      instanceLocator: 'YOUR INSTANCE LOCATOR',
      userId: this.props.currentUsername,
      tokenProvider: new Chatkit.TokenProvider({
        url: 'http://localhost:3001/authenticate',
      }),
    })

    chatManager
      .connect()
      .then(currentUser => {
        this.setState({ currentUser })
      })
      .catch(error => console.error('error', error))
  }

  render() {
-    return (
-      <div>
-        <h1>Chat</h1>
-      </div>
-    )
+    const styles = {
+      container: {
+        height: '100vh',
+        display: 'flex',
+        flexDirection: 'column',
+      },
+      chatContainer: {
+        display: 'flex',
+        flex: 1,
+      },
+      whosOnlineListContainer: {
+        width: '300px',
+        flex: 'none',
+        padding: 20,
+        backgroundColor: '#2c303b',
+        color: 'white',
+      },
+      chatListContainer: {
+        padding: 20,
+        width: '85%',
+        display: 'flex',
+        flexDirection: 'column',
+      },
+   }

+    return (
+      <div style={styles.container}>
+        <div style={styles.chatContainer}>
+          <aside style={styles.whosOnlineListContainer}>
+            <h2>Who's online PLACEHOLDER</h2>
+          </aside>
+          <section style={styles.chatListContainer}>
+            <h2>Chat PLACEHOLDER</h2>
+          </section>
+        </div>
+      </div>
+    )
  }
}

export default ChatScreen

If you run the app now, you'll see the basic layout take place:

Awesome!

Step 9. Subscribe to new messages

I am really excited to show you this!

Now we have a Chatkit connection, building chat features become as simple as hooking up Chatkit events to UI components. Here, let me show you.

First, create a stateless MessageList.js component in ./src/components:

+ import React, { Component } from 'react'
+
+ class MessagesList extends Component {
+   render() {
+     const styles = {
+       container: {
+         overflowY: 'scroll',
+         flex: 1,
+       },
+       ul: {
+         listStyle: 'none',
+       },
+       li: {
+         marginTop: 13,
+         marginBottom: 13,
+       },
+       senderUsername: {
+         fontWeight: 'bold',
+       },
+       message: { fontSize: 15 },
+     }
+     return (
+       <div
+         style={{
+           ...this.props.style,
+           ...styles.container,
+         }}
+       >
+         <ul style={styles.ul}>
+           {this.props.messages.map((message, index) => (
+             <li key={index} style={styles.li}>
+               <div>
+                 <span style={styles.senderUsername}>{message.senderId}</span>{' '}
+               </div>
+               <p style={styles.message}>{message.text}</p>
+             </li>
+           ))}
+         </ul>
+       </div>
+     )
+   }
+ }
+
+ export default MessagesList

Then update ChatScreen.js:

import React, { Component } from 'react'
import Chatkit from '@pusher/chatkit-client'
+import MessageList from './components/MessageList'


class ChatScreen extends Component {
  constructor(props) {
    super(props)
    this.state = {
      currentUser: {},
+     currentRoom: {},
+     messages: []
    }
  }

  componentDidMount () {
    const chatManager = new Chatkit.ChatManager({
      instanceLocator: 'YOUR INSTANCE LOCATOR',
      userId: this.props.currentUsername,
      tokenProvider: new Chatkit.TokenProvider({
        url: 'http://localhost:3001/authenticate',
      }),
    })

    chatManager
      .connect()
      .then(currentUser => {
        this.setState({ currentUser })
+        return currentUser.subscribeToRoom({
+          roomId: "YOUR ROOM ID",
+          messageLimit: 100,
+          hooks: {
+            onMessage: message => {
+              this.setState({
+                messages: [...this.state.messages, message],
+              })
+            },
+          },
+        })
+      })
+      .then(currentRoom => {
+        this.setState({ currentRoom })
+       })
      .catch(error => console.error('error', error))
  }

  render() {
    const styles = {
      ...
    }
    return (
      <div style={styles.container}>
        <div style={styles.chatContainer}>
          <aside style={styles.whosOnlineListContainer}>
            <h2>Who's online PLACEHOLDER</h2>
          </aside>
          <section style={styles.chatListContainer}>
-            <h2>Chat PLACEHOLDER</h2>
+            <MessageList
+              messages={this.state.messages}
+              style={styles.chatList}
+            />
          </section>
        </div>
      </div>
    )
  }
}

export default ChatScreen

Remember to replace YOUR ROOM ID with your own room ID that you noted earlier.

Let's break it down:

  • Once you connect to Chatkit you get a currentUser object that represents the current connected user
  • Chatkit is "user-driven" meaning that most if not all interactions happen on the currentUser
  • In this case, we call subscribeToRoom on the currentUser (currentUser.subscribeToRoom)
  • subscribeToRoom takes an event handler called onMessage that is called in real-time each time a new message arrives
  • Because we specified the messageLimit to be 100, onMessage is also called retroactively for up to 100 most recent messages. In practice, this means if you refresh the page you'll see up to 100 of the most recent chat messages
  • There is a fair amount of code here but once you break it down, all we're doing is taking new messages and updating the React state - the significant chat-related code couldn't be more minimal

Step 10. Sending messages

We're on a roll!

Next, let's allow users to send messages by first creating a SendMessageForm.js component in ./src/components:

+ import React, { Component } from 'react'
+
+ class SendMessageForm extends Component {
+   constructor(props) {
+     super(props)
+     this.state = {
+       text: '',
+     }
+     this.onSubmit = this.onSubmit.bind(this)
+     this.onChange = this.onChange.bind(this)
+   }
+
+   onSubmit(e) {
+     e.preventDefault()
+     this.props.onSubmit(this.state.text)
+     this.setState({ text: '' })
+   }
+
+   onChange(e) {
+     this.setState({ text: e.target.value })
+     if (this.props.onChange) {
+       this.props.onChange()
+     }
+   }
+
+   render() {
+     const styles = {
+       container: {
+         padding: 20,
+         borderTop: '1px #4C758F solid',
+         marginBottom: 20,
+       },
+       form: {
+         display: 'flex',
+       },
+       input: {
+         color: 'inherit',
+         background: 'none',
+         outline: 'none',
+         border: 'none',
+         flex: 1,
+         fontSize: 16,
+       },
+     }
+     return (
+       <div style={styles.container}>
+         <div>
+           <form onSubmit={this.onSubmit} style={styles.form}>
+             <input
+               type="text"
+               placeholder="Type a message here then hit ENTER"
+               onChange={this.onChange}
+               value={this.state.text}
+               style={styles.input}
+             />
+           </form>
+         </div>
+       </div>
+     )
+   }
+ }
+
+ export default SendMessageForm

Then - you guessed it - update ChatScreen.js:

import React, { Component } from 'react'
import Chatkit from '@pusher/chatkit-client'
import MessageList from './components/MessageList'
+ import SendMessageForm from './components/SendMessageForm'

class ChatScreen extends Component {
  constructor(props) {
    super(props)
    this.state = {
      currentUser: {},
      currentRoom: {},
      messages: []
    }
+    this.sendMessage = this.sendMessage.bind(this)
  }


+  sendMessage(text) {
+    this.state.currentUser.sendMessage({
+      text,
+      roomId: this.state.currentRoom.id,
+    })
+  }

 componentDidMount () {
    const chatManager = new Chatkit.ChatManager({
      instanceLocator: 'YOUR INSTANCE LOCATOR',
      userId: this.props.currentUsername,
      tokenProvider: new Chatkit.TokenProvider({
        url: 'http://localhost:3001/authenticate',
      }),
    })

    chatManager
      .connect()
      .then(currentUser => {
        this.setState({ currentUser })
        return currentUser.subscribeToRoom({
          roomId: YOUR ROOM ID,
          messageLimit: 100,
          hooks: {
            onMessage: message => {
              this.setState({
                messages: [...this.state.messages, message],
              })
            },
          },
        })
      })
      .then(currentRoom => {
        this.setState({ currentRoom })
       })
      .catch(error => console.error('error', error))
  }


  render() {
    const styles = {
     ...
    }
    return (
      <div style={styles.container}>
        <div style={styles.chatContainer}>
          <aside style={styles.whosOnlineListContainer}>
            <h2>Who's online PLACEHOLDER</h2>
          </aside>
          <section style={styles.chatListContainer}>
            <MessageList
              messages={this.state.messages}
              style={styles.chatList}
            />
+           <SendMessageForm onSubmit={this.sendMessage} />
          </section>
        </div>
      </div>
    )
  }
}

export default ChatScreen

The SendMessageForm component is essentially the same as theWhatIsYourUsernameForm component we defined earlier.

When the SendMessageForm is submitted, we access this.state.currentUser and call sendMessage (remember, most interactions happen on currentUser)

You can probably see a pattern emerging...

ChatScreen is a container component that manages our application state and renders the UI using presentational - normally stateless - components. Most of our code involves hooking up Chatkit events and their associated data to React UI components.

Step 11. Add realtime typing indicators

If you've ever attempted to implement your own typing indicators, you'll know it can be tricky. In general, more real-time features means more data and more connections to manage.

With Chatkit, you can add typing indicators with little effort.

Start by creating a TypingIndicator.js component in ./src/components:

+import React, { Component } from 'react'
+
+class TypingIndicator extends Component {
+  render() {
+    if (this.props.usersWhoAreTyping.length > 0) {
+      return (
+        <div>
+          {`${this.props.usersWhoAreTyping
+            .slice(0, 2)
+            .join(' and ')} is typing`}
+        </div>
+      )
+    }
+    return <div />
+  }
+}
+
+export default TypingIndicator

Then update ChatScreen.js:

import React, { Component } from 'react'
import Chatkit from '@pusher/chatkit-client'
import MessageList from './components/MessageList'
import SendMessageForm from './components/SendMessageForm'
+import TypingIndicator from './components/TypingIndicator'

class ChatScreen extends Component {
  constructor(props) {
    super(props)
    this.state = {
      currentUser: {},
      currentRoom: {},
      messages: [],
+     usersWhoAreTyping: [],
    }
    this.sendMessage = this.sendMessage.bind(this)
+   this.sendTypingEvent = this.sendTypingEvent.bind(this)
  }

+  sendTypingEvent() {
+    this.state.currentUser
+      .isTypingIn({ roomId: this.state.currentRoom.id })
+      .catch(error => console.error('error', error))
+  }

  sendMessage(text) {
    this.state.currentUser.sendMessage({
      text,
      roomId: this.state.currentRoom.id,
    })
  }

  componentDidMount() {
    const chatManager = new Chatkit.ChatManager({
      instanceLocator: 'YOUR INSTANCE LOCATOR',
      userId: this.props.currentUsername,
      tokenProvider: new Chatkit.TokenProvider({
        url: 'http://localhost:3001/authenticate',
      }),
    })

    chatManager
      .connect()
      .then(currentUser => {
        this.setState({ currentUser })
        return currentUser.subscribeToRoom({
          roomId: YOUR ROOM ID,
          messageLimit: 100,
          hooks: {
            onMessage: message => {
              this.setState({
                messages: [...this.state.messages, message],
              })
            },
+            onUserStartedTyping: user => {
+              this.setState({
+                usersWhoAreTyping: [...this.state.usersWhoAreTyping, user.name],
+             })
+            },
+            onUserStoppedTyping: user => {
+              this.setState({
+                usersWhoAreTyping: this.state.usersWhoAreTyping.filter(
+                  username => username !== user.name
+                ),
+              })
+            },
          },
        })
      })
      .then(currentRoom => {
        this.setState({ currentRoom })
      })
      .catch(error => console.error('error', error))
  }

  render() {
    const styles = {
      ...
    }
    return (
      <div style={styles.container}>>
        <div style={styles.chatContainer}>
          <aside style={styles.whosOnlineListContainer}>
            <h2>Who's online PLACEHOLDER</h2>
          </aside>
          <section style={styles.chatListContainer}>
            <MessageList
              messages={this.state.messages}
              style={styles.chatList}
            />
+           <TypingIndicator usersWhoAreTyping={this.state.usersWhoAreTyping} />
            <SendMessageForm
              onSubmit={this.sendMessage}
+             onChange={this.sendTypingEvent}
            />
          </section>
        </div>
      </div>
    )
  }
}

export default ChatScreen

When using Chatkit, typing indicators boil down to two fundamental actions:

  • Calling currentUser.userIsTyping when the current user starts typing; then,
  • listening to userStartedTyping and userStoppedTyping events

And that is pretty much it.

"But Alex, what about when the user stops typing?"

That is a very good question.

Chatkit is intelligent like that. If the service doesn't receive a userIsTyping event after a few seconds, it assumes the currentUser has stopped typing. Therefore, there is no need to manually raise an event when someone stops typing. Pretty slick, right?

Step 12. Add a "Who's online" list

Can you feel the momentum? Almost done now 🙌

To finish up the chat app, let's use Chatkit's "who's online" feature to render a list of users and their real-time online status.

Start by creating a WhosOnlineList.js component in /src/components:

+import React, { Component } from 'react'
+
+class WhosOnlineList extends Component {
+  renderUsers() {
+    return (
+      <ul>
+        {this.props.users.map((user, index) => {
+          if (user.id === this.props.currentUser.id) {
+            return (
+              <WhosOnlineListItem key={index} presenceState="online">
+                {user.name} (You)
+              </WhosOnlineListItem>
+            )
+          }
+          return (
+            <WhosOnlineListItem key={index} presenceState={user.presence.state}>
+              {user.name}
+            </WhosOnlineListItem>
+          )
+        })}
+      </ul>
+    )
+  }
+
+  render() {
+    if (this.props.users) {
+      return this.renderUsers()
+    } else {
+      return <p>Loading...</p>
+    }
+  }
+}
+
+class WhosOnlineListItem extends Component {
+  render() {
+    const styles = {
+      li: {
+        display: 'flex',
+        alignItems: 'center',
+        marginTop: 5,
+        marginBottom: 5,
+        paddingTop: 2,
+        paddingBottom: 2,
+      },
+      div: {
+        borderRadius: '50%',
+        width: 11,
+        height: 11,
+        marginRight: 10,
+      },
+    }
+    return (
+      <li style={styles.li}>
+        <div
+          style={{
+            ...styles.div,
+            backgroundColor:
+              this.props.presenceState === 'online' ? '#539eff' : '#414756',
+          }}
+        />
+        {this.props.children}
+      </li>
+    )
+  }
+}
+
+export default WhosOnlineList

Then - for the last time 😢👋 - update ChatScreen.js:

import React, { Component } from 'react'
import Chatkit from '@pusher/chatkit-client'
import MessageList from './components/MessageList'
import SendMessageForm from './components/SendMessageForm'
import TypingIndicator from './components/TypingIndicator'
+import WhosOnlineList from './components/WhosOnlineList'

class ChatScreen extends Component {
  constructor(props) {
    super(props)
    this.state = {
      currentUser: {},
      currentRoom: {},
      messages: [],
      usersWhoAreTyping: [],
    }
    this.sendMessage = this.sendMessage.bind(this)
    this.sendTypingEvent = this.sendTypingEvent.bind(this)
  }

  sendTypingEvent() {
    this.state.currentUser
      .isTypingIn(this.state.currentRoom.id)
      .catch(error => console.error('error', error))
  }

   sendMessage(text) {
    this.state.currentUser.sendMessage({
      text,
      roomId: this.state.currentRoom.id,
    })
  }

  comonentDidMount() {
    const chatManager = new Chatkit.ChatManager({
      instanceLocator: 'YOUR INSTANCE LOCATOR',
      userId: this.props.currentUsername,
      tokenProvider: new Chatkit.TokenProvider({
        url: 'http://localhost:3001/authenticate',
      }),
    })

    chatManager
      .connect()
      .then(currentUser => {
        this.setState({ currentUser })
        return currentUser.subscribeToRoom({
          roomId: YOUR ROOM ID,
          messageLimit: 100,
          hooks: {
            newMessage: message => {
              this.setState({
                messages: [...this.state.messages, message],
              })
            },
            userStartedTyping: user => {
              this.setState({
                usersWhoAreTyping: [...this.state.usersWhoAreTyping, user.name],
              })
            },
            userStoppedTyping: user => {
              this.setState({
                usersWhoAreTyping: this.state.usersWhoAreTyping.filter(
                  username => username !== user.name
                ),
              })
            },
+            onPresenceChange: () => this.forceUpdate(),
+            onUserJoined: () => this.forceUpdate(),
+          },
        })
      })
      .then(currentRoom => {
        this.setState({ currentRoom })
      })
      .catch(error => console.error('error', error))
  }

  render() {
    const styles = {
      ...
    }
    return (
      <div style={styles.container}>
        <header style={styles.header}>
          <h2>Chatly</h2>
        </header>
        <div style={styles.chatContainer}>
          <aside style={styles.whosOnlineListContainer}>
-            <h2>Who's online PLACEHOLDER</h2>
+            <WhosOnlineList
+              currentUser={this.state.currentUser}
+              users={this.state.currentRoom.users}
+            />
          </aside>
          <section style={styles.chatListContainer}>
            <MessageList
              messages={this.state.messages}
              style={styles.chatList}
            />
            <TypingIndicator usersWhoAreTyping={this.state.usersWhoAreTyping} />
            <SendMessageForm
              onSubmit={this.sendMessage}
              onChange={this.sendTypingEvent}
            />
          </section>
        </div>
      </div>
    )
  }
}

export default ChatScreen

Managing the state of your users in React state can be a bit tricky so we manage it for you in currentRoom.users.

As users connect and disconnect, this property is dynamically updated. In other words, currentRoom.users should always refelect the current state of your chat app.

Therefore, when users come online or go offline (onPresenceChange), or new users join (onUserAdded) all we have to do is call forceUpdate which tells React to evaluate currentRoom.users and update the UI.

Again, it really boils down to wiring some simple data and events to React components and that's all, folks!

Conclusion

In this walkthrough, you built a complete chat application with

  • group chat;
  • a “Who’s online” list; and,
  • typing indicators

Because we used Chatkit, we also get some bonus features for free:

  • message history (refresh the page and you’ll see up to 100 of the most recent messages);
  • reliability in the case that the client temporarily loses connection (Chatkit handles disconnects gracefully); and,
  • the ability to scale without needing to worry about infrastructure

We wrote a fair amount of code, but none of it was particularly complicated.

Chatkit has a minimal but powerful API that manages all our chat data for us. All we had to do is take that data and render it for the user.

Want to keep building? Why not add rich media support and read receipts? Chatkit supports both:

You may also be interested in checking out our powerful Chatkit Slack demo (250+ stars ⭐️). It’s similar to the application we just built but more complete.

What will you build with Chatkit? We'd love to see! Your feedback guides us in improving Chatkit. Let us know what helps you reach your goals, what’s getting in your way, or what’s missing.