Building a Notion-like system with Socket.io And React 😍
Tags: javascript, webdev, react, opensource
Published: 2022-10-24 12:30:48

## What is this article about?
We are going to build a **knowledge** system like Click-Up and Notion. You will be able to add posts, write comments, tag other users and show it in their notifications.
In notion users can see what other users do in real-time without refreshing the page. This is why we will be using Socket.io. In the next article I will write about SSE (server sent events)

![Knowledge](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/e6aeqifnxvhywz2jebvw.gif)

## What is WebSocket?

WebSocket is a built-in Node.js module that enables us to create a real-time connection between a client and a server, allowing them to send data in both ways. However, WebSocket is low-level and doesn't provide the functionalities required to build complex real-time applications; this is why Socket.io exists.

[Socket.io](https://socket.io/) is a popular JavaScript library that allows us to create real-time, bi-directional communication between software applications and a Node.js server. It is optimised to process a large volume of data with minimal delay and provides better functionalities, such as fallback to HTTP long-polling or automatic reconnection.

## Novu - the first open-source notification infrastructure
Just a quick background about us. Novu is the first open-source [notification infrastructure](https://novu.co). We basically help to manage all the product notifications. It can be **In-App** (the bell icon like you have in the Dev Community - **Websockets**), Emails, SMSs and so on.

I would be super grateful if you can help us out by starring the library 🤩
[https://github.com/novuhq/novu](https://github.com/novuhq/novu)

[![GitHub](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/imvcgndr0j0138n89fzw.png)](https://github.com/novuhq/novu)

## How to create a real-time connection with React & Socket.io

Here, we'll set up the project environment for the notion app. You'll also learn how to add Socket.io to a React and Node.js application and connect both development servers for real-time communication via [Socket.io](https://socket.io/).

Create the project folder containing two sub-folders named client and server.

```bash
mkdir notion-platform
cd notion-platform
mkdir client server
```

Navigate into the client folder via your terminal and create a new React.js project.

```bash
cd client
npx create-react-app ./
```

Install Socket.io client API and React Router. [React Router](https://reactrouter.com/docs/en/v6) is a JavaScript library that enables us to navigate between pages in a React application.

```bash
npm install socket.io-client react-router-dom
```

Delete the redundant files such as the logo and the test files from the React app, and update the App.js file to display Hello World as below.

```jsx
function App() {
	return (
		<div>
			<p>Hello World!</p>
		</div>
	);
}
export default App;
```

Add the Socket.io client API to the React app as below:

```jsx
import { io } from "socket.io-client";

//👇🏻 http://localhost:4000 is where the server host URL.
const socket = io.connect("http://localhost:4000");

function App() {
	return (
		<div>
			<p>Hello World!</p>
		</div>
	);
}
export default App;
```

Navigate into the server folder and create a package.json file.

```bash
cd server & npm init -y
```

Install Express.js, CORS, Nodemon, and Socket.io Server API.

```bash
npm install express cors nodemon socket.io
```

[Express.js](https://expressjs.com/) is a fast, minimalist framework that provides several features for building web applications in Node.js. [CORS](https://www.npmjs.com/package/cors) is a Node.js package that allows communication between different domains.

[Nodemon](https://www.npmjs.com/package/nodemon) is a Node.js tool that automatically restarts the server after detecting file changes, and [Socket.io](https://socket.io/docs/v4/server-api/) allows us to configure a real-time connection on the server.

Create an index.js file - the entry point to the web server.

```bash
touch index.js
```

Set up a Node.js server using Express.js. The code snippet below returns a JSON object when you visit the [`http://localhost:4000/api`](http://localhost:4000/api) in your browser.

```jsx
//👇🏻index.js
const express = require("express");
const app = express();
const PORT = 4000;

app.use(express.urlencoded({ extended: true }));
app.use(express.json());

app.get("/api", (req, res) => {
	res.json({
		message: "Hello world",
	});
});

app.listen(PORT, () => {
	console.log(`Server listening on ${PORT}`);
});
```

Import the HTTP and the CORS library to allow data transfer between the client and the server domains.

```jsx
const express = require("express");
const app = express();
const PORT = 4000;

//👇🏻 New imports
const http = require("http").Server(app);
const cors = require("cors");

app.use(express.urlencoded({ extended: true }));
app.use(express.json());
app.use(cors());

app.get("/api", (req, res) => {
	res.json({
		message: "Hello world",
	});
});

http.listen(PORT, () => {
	console.log(`Server listening on ${PORT}`);
});
```

Next, add Socket.io to the project to create a real-time connection. Before the `app.get()` block, copy the code below.

```jsx
//👇🏻 New imports
.....
const socketIO = require('socket.io')(http, {
    cors: {
        origin: "http://localhost:3000"
    }
});

//👇🏻 Add this before the app.get() block
socketIO.on('connection', (socket) => {
    console.log(`⚡: ${socket.id} user just connected!`);

    socket.on('disconnect', () => {
      socket.disconnect()
      console.log('🔥: A user disconnected');
    });
});
```

From the code snippet above, the `socket.io("connection")` function establishes a connection with the React app, then creates a unique ID for each socket and logs the ID to the console whenever a user visits the web page.

When you refresh or close the web page, the socket fires the disconnect event showing that a user has disconnected from the socket.

Configure Nodemon by adding the start command to the list of scripts in the `package.json` file. The code snippet below starts the server using Nodemon.

```jsx
//👇🏻 In server/package.json"
"scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon index.js"
}
```

You can now run the server with Nodemon by using the command below.

```bash
npm start
```

## Building the user interface

Here, we'll create the user interface for the notion application to enable users to sign in, write posts, add comments, and tag other users.

Navigate into the `client/src` folder and create a components folder containing `Login.js`, `Home.js`, `CreatePost.js`, and `NotionPost.js` files.

```bash
cd client
mkdir components
cd components
touch Login.js Home.js CreatePost.js NotionPost.js
```

Update the `App.js` file to render the newly created components on different routes via React Router as below:

```jsx
import { BrowserRouter, Routes, Route } from "react-router-dom";
import NotionPost from "./components/NotionPost";
import CreatePost from "./components/CreatePost";
import Home from "./components/Home";
import Login from "./components/Login";
import { io } from "socket.io-client";

const socket = io.connect("http://localhost:4000");

function App() {
	return (
		<BrowserRouter>
			<Routes>
				<Route path='/' element={<Login socket={socket} />} />
				<Route path='/dashboard' element={<Home socket={socket} />} />
				<Route path='/post/create' element={<CreatePost socket={socket} />} />
				<Route path='/post/:id' element={<NotionPost socket={socket} />} />
			</Routes>
		</BrowserRouter>
	);
}

export default App;
```

Navigate into the `src/index.css` file and copy the code below. It contains all the CSS required for styling this project.

```css
@import url("https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@300;400;500;600;700&display=swap");
* {
	box-sizing: border-box;
	padding: 0;
	margin: 0;
	font-family: "Space Grotesk", sans-serif;
}
body {
	padding: 0;
}
.login {
	width: 100%;
	min-height: 100vh;
	display: flex;
	flex-direction: column;
	align-items: center;
	justify-content: center;
}
.login > h2 {
	color: #00abb3;
	margin-bottom: 30px;
}
.loginForm {
	width: 70%;
	display: flex;
	flex-direction: column;
}
.loginForm > input {
	margin: 10px 0;
	padding: 10px 15px;
}
.home__navbar {
	width: 100%;
	height: 10vh;
	padding: 20px;
	display: flex;
	align-items: center;
	justify-content: space-between;
	border-bottom: 1px solid #eaeaea;
}
.home__navbar > h2 {
	color: #00abb3;
}
.home__buttons {
	display: flex;
	align-items: center;
	justify-content: baseline;
}
.home__createBtn {
	padding: 10px;
	cursor: pointer;
	margin-right: 10px;
	background-color: #00abb3;
	border: none;
	outline: none;
	color: #fff;
}
.home__createBtn:hover,
.createForm__button:hover {
	background-color: #02595e;
}
.home__notifyBtn {
	padding: 10px;
	cursor: pointer;
	color: #00abb3;
	background-color: #fff;
	border: 1px solid #3c4048;
	outline: none;
	width: 100px;
}
.posts__container {
	width: 100%;
	min-height: 90vh;
	padding: 30px 20px;
}
.post {
	width: 100%;
	min-height: 8vh;
	background-color: #00abb3;
	border-radius: 5px;
	padding: 20px;
	display: flex;
	color: #eaeaea;
	align-items: center;
	justify-content: space-between;
	margin-bottom: 15px;
}
.post__cta {
	padding: 10px;
	background-color: #fff;
	cursor: pointer;
	outline: none;
	border: none;
	border-radius: 2px;
}
.createPost {
	min-height: 100vh;
	width: 100%;
	padding: 30px 20px;
}
.createPost > h2 {
	text-align: center;
	color: #00abb3;
}
.createForm {
	width: 100%;
	min-height: 80vh;
	padding: 20px;
	display: flex;
	flex-direction: column;
}
.createForm__title {
	padding: 10px;
	height: 45px;
	margin-bottom: 10px;
	text-transform: capitalize;
	border: 1px solid #3c4048;
}
.createForm__content {
	padding: 15px;
	margin-bottom: 15px;
	border: 1px solid #3c4048;
}
.createForm__button {
	width: 200px;
	padding: 10px;
	height: 45px;
	background-color: #00abb3;
	color: #fff;
	outline: none;
	border: none;
	cursor: pointer;
	border-radius: 5px;
}
.notionPost {
	width: 100%;
	min-height: 100vh;
	background-color: #eaeaea;
	display: flex;
	flex-direction: column;
	padding: 30px 50px;
}
.notionPost__container {
	width: 90%;
	min-height: 70vh;
	margin-bottom: 30px;
}
.notionPost__author {
	color: #00abb3;
}
.notionPost__date {
	opacity: 0.4;
	font-size: 12px;
}
.notionPost__content {
	padding-top: 30px;
	line-height: 200%;
}
.comments__container {
	min-height: 70vh;
	border: 1px solid #3c4048;
	padding: 30px;
	box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.05), 2px 2px 3px 1px rgba(208, 213, 219, 0.28);
	border-radius: 3px;
}
.comments__inputContainer {
	display: flex;
	align-items: center;
	margin: 30px 0;
}
.comments__input {
	width: 50%;
	padding: 15px;
	margin-right: 15px;
}
.comments__cta,
.login__cta {
	padding: 15px;
	width: 200px;
	cursor: pointer;
	outline: none;
	border: none;
	background-color: #00abb3;
	color: #fff;
}
.comment {
	margin-bottom: 15px;
}
```

### The Login page

Here, the application accepts the username and saves it in the local storage for user identification. Copy the code below into the Login component.

```jsx
import React, { useState } from "react";
import { useNavigate } from "react-router-dom";

const Login = () => {
	const [username, setUsername] = useState("");
	const navigate = useNavigate();

	const handleLogin = (e) => {
		e.preventDefault();
		//The username 👉🏻 console.log({ username });
		localStorage.setItem("username", username);
		navigate("/dashboard");
	};
	return (
		<div className='login'>
			<h2>Sign in to HackNotion</h2>
			<form className='loginForm' onSubmit={handleLogin}>
				<label htmlFor='username'>Enter your username</label>
				<input
					name='username'
					id='username'
					type='text'
					value={username}
					required
					onChange={(e) => setUsername(e.target.value)}
				/>
				<button className='login__cta'>LOG IN</button>
			</form>
		</div>
	);
};

export default Login;
```

### The Home page

Copy the code below into the `Home.js` file. It represents the home layout for the application.

```jsx
import React from "react";
import { useNavigate } from "react-router-dom";

const Home = () => {
	const navigate = useNavigate();

	const createPostBtn = () => navigate("/post/create");
	const readMoreBtn = () => navigate("/post/:id");

	return (
		<div className='home'>
			<nav className='home__navbar'>
				<h2>HackNotion</h2>
				<div className='home__buttons'>
					<button className='home__createBtn' onClick={createPostBtn}>
						CREATE POST
					</button>
					<button className='home__notifyBtn'>NOTIFY</button>
				</div>
			</nav>

			<div className='posts__container'>
				<div className='post'>
					<h3>How to create a new Socket.io client</h3>
					<button className='post__cta' onClick={readMoreBtn}>
						READ MORE
					</button>
				</div>

				<div className='post'>
					<h3>Creating React Native project with Expo</h3>
					<button className='post__cta' onClick={readMoreBtn}>
						READ MORE
					</button>
				</div>
			</div>
		</div>
	);
};

export default Home;
```

![Notion Post](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/132tbhxsikwk1cktec3z.png)

### The NotionPost page

This page is dynamic and displays the content of each post via the ID passed into the URL. Here, users can read the notion post and add comments.

Copy the code below into the `NotionPost.js` file:

```jsx
import React, { useState } from "react";

const NotionPost = () => {
	const [comment, setComment] = useState("");

	const handleAddComment = (e) => {
		e.preventDefault();
		console.log({ comment });
		setComment("");
	};

	return (
		<div className='notionPost'>
			<div className='notionPost__container'>
				<h1>How to create a new React Native project with Expo</h1>
				<div className='notionPost__meta'>
					<p className='notionPost__author'>By Nevo David</p>
					<p className='notionPost__date'>Created on 22nd September, 2022</p>
				</div>

				<div className='notionPost__content'>
					For this article, I will use Puppeteer and ReactJS. Puppeteer is a
					Node.js library that automates several browser actions such as form
					submission.
				</div>
			</div>

			<div className='comments__container'>
				<h2>Add Comments</h2>
				<form className='comments__inputContainer' onSubmit={handleAddComment}>
					<textarea
						placeholder='Type in your comments...'
						rows={5}
						className='comments__input'
						value={comment}
						required
						onChange={(e) => setComment(e.target.value)}
					/>
					<button className='comments__cta'>Add Comment</button>
				</form>

				<div>
					<p className='comment'>
						<span style={{ fontWeight: "bold" }}>Scopsy Dima</span> - Nice post
						fam!❤️
					</p>
				</div>
			</div>
		</div>
	);
};

export default NotionPost;
```

![CreatePost Page](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/odum938c3iyztaordlr7.gif)


### The CreatePost page

Here, we'll create a simple layout that allows users to create posts by adding the title and its content. Users will also be able to tag other users using [React Tag](https://www.npmjs.com/package/react-tag-input).

> [React Tag](https://www.npmjs.com/package/react-tag-input) is a library that allows us to create tags easily via a single component. It provides several features, such as autocomplete based on a suggestion list, reordering using drag-and-drop, and many more.*

Copy the code below into the `CreatePost.js` file.

```jsx
import React, { useState } from "react";
import { useNavigate } from "react-router-dom";

const CreatePost = () => {
	const navigate = useNavigate();

	const [postTitle, setPostTitle] = useState("");
	const [postContent, setPostContent] = useState("");

	//...gets the publish date for the post
	const currentDate = () => {
		const d = new Date();
		return `${d.getDate()}-${d.getMonth() + 1}-${d.getFullYear()}`;
	};

	//...logs the post details to the console
	const addPost = (e) => {
		e.preventDefault();
		console.log({
			postTitle,
			postContent,
			username: localStorage.getItem("username"),
			timestamp: currentDate(),
		});
		navigate("/dashboard");
	};

	return (
		<>
			<div className='createPost'>
				<h2>Create a new Post</h2>
				<form className='createForm' onSubmit={addPost}>
					<label htmlFor='title'> Title</label>
					<input
						type='text'
						required
						value={postTitle}
						onChange={(e) => setPostTitle(e.target.value)}
						className='createForm__title'
					/>

					<label htmlFor='title'> Content</label>
					<textarea
						required
						rows={15}
						value={postContent}
						onChange={(e) => setPostContent(e.target.value)}
						className='createForm__content'
					/>

					<button className='createForm__button'>ADD POST</button>
				</form>
			</div>
		</>
	);
};

export default CreatePost;
```

Import React Tags into the `CreatePost.js` file:

```jsx
import { WithContext as ReactTags } from "react-tag-input";
```

Update the CreatePost component to contain the code snippet below for creating tags with React Tags.

```jsx
//👇🏻 The suggestion list for autocomplete
const suggestions = ["Tomer", "David", "Nevo"].map((name) => {
	return {
		id: name,
		text: name,
	};
});

const KeyCodes = {
	comma: 188,
	enter: 13,
};
//👇🏻 The comma and enter keys are used to separate each tags
const delimiters = [KeyCodes.comma, KeyCodes.enter];

//...The React component
const CreatePost = () => {
	//👇🏻 An array containing the tags
	const [tags, setTags] = useState([]);

	//...deleting tags
	const handleDelete = (i) => {
		setTags(tags.filter((tag, index) => index !== i));
	};

	//...adding new tags
	const handleAddition = (tag) => {
		setTags([...tags, tag]);
	};

	//...runs when you click on a tag
	const handleTagClick = (index) => {
		console.log("The tag at index " + index + " was clicked");
	};

	return (
		<div className='createPost'>
			<form>
				{/**...below the input fields---*/}
				<ReactTags
					tags={tags}
					suggestions={suggestions}
					delimiters={delimiters}
					handleDelete={handleDelete}
					handleAddition={handleAddition}
					handleTagClick={handleTagClick}
					inputFieldPosition='bottom'
					autocomplete
				/>
				<button className='createForm__button'>ADD POST</button>
			</form>
		</div>
	);
};

export default CreatePost;
```

React Tags also allows us to customize its elements. Add the following code to the `src/index.css` file:

```jsx
/*
You can learn how it's styled here: 
https://stackblitz.com/edit/react-tag-input-1nelrc
*/
.ReactTags__tags react-tags-wrapper,
.ReactTags__tagInput {
	width: 100%;
}
.ReactTags__selected span.ReactTags__tag {
	border: 1px solid #ddd;
	background: #00abb3;
	color: white;
	font-size: 12px;
	display: inline-block;
	padding: 5px;
	margin: 0 5px;
	border-radius: 2px;
	min-width: 100px;
}

.ReactTags__selected button.ReactTags__remove {
	color: #fff;
	margin-left: 15px;
	cursor: pointer;
	background-color: orangered;
	padding: 0 10px;
	border: none;
	outline: none;
}

.ReactTags__tagInput input.ReactTags__tagInputField,
.ReactTags__tagInput input.ReactTags__tagInputField:focus {
	margin: 10px 0;
	font-size: 12px;
	width: 100%;
	padding: 10px;
	height: 45px;
	text-transform: capitalize;
	border: 1px solid #3c4048;
}

.ReactTags__selected span.ReactTags__tag {
	border: 1px solid #ddd;
	background: #63bcfd;
	color: white;
	font-size: 12px;
	display: inline-block;
	padding: 5px;
	margin: 0 5px;
	border-radius: 2px;
}
.ReactTags__selected a.ReactTags__remove {
	color: #aaa;
	margin-left: 5px;
	cursor: pointer;
}

/* Styles for suggestions */
.ReactTags__suggestions {
	position: absolute;
}
.ReactTags__suggestions ul {
	list-style-type: none;
	box-shadow: 0.05em 0.01em 0.5em rgba(0, 0, 0, 0.2);
	background: white;
	width: 200px;
}
.ReactTags__suggestions li {
	border-bottom: 1px solid #ddd;
	padding: 5px 10px;
	margin: 0;
}
.ReactTags__suggestions li mark {
	text-decoration: underline;
	background: none;
	font-weight: 600;
}
.ReactTags__suggestions ul li.ReactTags__activeSuggestion {
	background: #fff;
	cursor: pointer;
}

.ReactTags__remove {
	border: none;
	cursor: pointer;
	background: none;
	color: white;
}
```

Congratulations! We've completed the layout for the notion application. Next, let's learn how to add all the needed functionalities with the Socket.io Node.js server.

## Creating new posts with Socket.io

In this section, I'll guide you on how to create new posts and display them on the React app with Socket.io.

Update the `addPost` function within the `CreatePost` component by sending the newly created post to the server via Socket.io.

```jsx
//👇🏻 Socket.io was passed from the App.js file
const CreatePost = ({ socket }) => {
	//...other functions

	const addPost = (e) => {
		e.preventDefault();

		//👇🏻 sends all the post details to the server
		socket.emit("createPost", {
			postTitle,
			postContent,
			username: localStorage.getItem("username"),
			timestamp: currentDate(),
			tags,
		});
		navigate("/dashboard");
	};

	return <div className='createPost'>...</div>;
};
```

Create a listener to the event on the server.

```jsx
socketIO.on("connection", (socket) => {
	console.log(`⚡: ${socket.id} user just connected!`);

	socket.on("createPost", (data) => {
		/*👇🏻 data - contains all the post details 
			 from the React app
		*/
		console.log(data);
	});

	socket.on("disconnect", () => {
		socket.disconnect();
		console.log("🔥: A user disconnected");
	});
});
```

Create an array on the backend server that holds all the posts, and add the new post to the list.

```jsx
//👇🏻 generates a random ID
const fetchID = () => Math.random().toString(36).substring(2, 10);

let notionPosts = [];

socket.on("createPost", (data) => {
	const { postTitle, postContent, username, timestamp, tags } = data;
	notionPosts.unshift({
		id: fetchID(),
		title: postTitle,
		author: username,
		createdAt: timestamp,
		content: postContent,
		comments: [],
	});
	//👉🏻 We'll use the tags later for sending notifications

	//👇🏻 The notionposts are sent back to the React app via another event
	socket.emit("updatePosts", notionPosts);
});
```

Add a listener to the notion posts on the React app via the useEffect hook by copying the code below:

```jsx
//👇🏻 Within Home.js file

useEffect(() => {
	socket.on("updatePosts", (posts) => console.log(posts));
}, [socket]);
```

## Displaying the posts

Save the posts into a state and render them as below:

```jsx
import React, { useEffect, useState } from "react";
import { useNavigate } from "react-router-dom";

const Home = ({ socket }) => {
	const navigate = useNavigate();
	const [posts, setPosts] = useState([]);

	//👇🏻 Saves the posts into the "posts" state
	useEffect(() => {
		socket.on("updatePosts", (posts) => setPosts(posts));
	}, [socket]);

	const createPostBtn = () => navigate("/post/create");

	//👇🏻 Navigates to the NotionPost page to view
	//   all the post contents
	const readMoreBtn = (postID) => {
		navigate(`/post/${postID}`);
	};

	return (
		<div className='home'>
			<nav className='home__navbar'>
				<h2>HackNotion</h2>
				<div className='home__buttons'>
					<button className='home__createBtn' onClick={createPostBtn}>
						CREATE POST
					</button>
					<button className='home__notifyBtn'>NOTIFY</button>
				</div>
			</nav>

			<div className='posts__container'>
				{posts?.map((post) => (
					<div className='post' key={post.id}>
						<h3>{post.title}</h3>
						<button className='post__cta' onClick={() => readMoreBtn(post.id)}>
							READ MORE
						</button>
					</div>
				))}
			</div>
		</div>
	);
};

export default Home;
```

So far, we can only view the posts when we add one. Next, let's make it possible for us to display the posts when we load the page.

Create a route on the server that returns the notion posts.

```jsx
app.get("/api", (req, res) => {
	res.json(notionPosts);
});
```

Update the `Home.js` file fetch the notion posts and listen for new posts from the server.

```jsx
useEffect(() => {
	function fetchPosts() {
		fetch("http://localhost:4000/api")
			.then((res) => res.json())
			.then((data) => setPosts(data))
			.catch((err) => console.error(err));
	}
	fetchPosts();
}, []);

useEffect(() => {
	socket.on("updatePosts", (posts) => setPosts(posts));
}, [socket]);
```

## Completing the Notion Post component

In the previous section, you learnt how to create and display notion posts to users. Here, you'll learn how to show the contents of each notion post when you click the Read More button.


![Read More](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/c22pvj625bt3tqvr7yx8.gif)


Update the `readMoreBtn` function within the `Home.js` file as below:

```jsx
const readMoreBtn = (postID) => {
	socket.emit("findPost", postID);
//👇🏻 navigates to the Notionpost routenavigate(`/post/${postID}`);
};
```

The code snippet above gets the ID of the selected post and sends a Socket.io event containing the post ID to the server before redirecting to the post route.

Create a listener to the `findPost` event and return the post details via another Socket.io event.

```jsx
socket.on("findPost", (postID) => {

  //👇🏻 Filter the notion post via the post ID
  let result = notionPosts.filter((post) => post.id === postID);

  //👇🏻 Returns a new event containing the post details
	socket.emit("postDetails", result[0]);
});
```

Listen to the `postDetails` event with the `NotionPost` component and render the post details as below:

```jsx
import React, { useState, useEffect } from "react";
import { useParams } from "react-router-dom";

const NotionPost = ({ socket }) => {
	//👇🏻 gets the Post ID from its URL
	const { id } = useParams();

	const [comment, setComment] = useState("");
	const [post, setPost] = useState({});

	//👇🏻loading state for async request
	const [loading, setLoading] = useState(true);

	//👇🏻 Gets the post details from the server for display
	useEffect(() => {
		socket.on("postDetails", (data) => {
			setPost(data);
			setLoading(false);
		});
	}, [socket]);

	//👇🏻 Function for creating new comments
	const handleAddComment = (e) => {
		e.preventDefault();
		console.log("newComment", {
			comment,
			user: localStorage.getItem("username"),
			postID: id,
		});
		setComment("");
	};

	if (loading) {
		return <h2>Loading... Please wait</h2>;
	}

	return (
		<div className='notionPost'>
			<div className='notionPost__container'>
				<h1>{post.title}</h1>
				<div className='notionPost__meta'>
					<p className='notionPost__author'>By {post.author}</p>
					<p className='notionPost__date'>Created on {post.createdAt}</p>
				</div>

				<div className='notionPost__content'>{post.content}</div>
			</div>

			<div className='comments__container'>
				<h2>Add Comments</h2>
				<form className='comments__inputContainer' onSubmit={handleAddComment}>
					<textarea
						placeholder='Type in your comments...'
						rows={5}
						className='comments__input'
						value={comment}
						required
						onChange={(e) => setComment(e.target.value)}
					/>
					<button className='comments__cta'>Add Comment</button>
				</form>

				<div>
					<p className='comment'>
						<span style={{ fontWeight: "bold" }}>Scopsy Dima</span> - Nice post
						fam!❤️
					</p>
				</div>
			</div>
		</div>
	);
};

export default NotionPost;
```

### The Comments section

Here, I'll guide you through adding comments to each notion post and displaying them in real-time.

Update the `handleAddComment` function within the `NotionPost` component to send the new comments details to the server.

```jsx
const handleAddComment = (e) => {
	e.preventDefault();
	socket.emit("newComment", {
		comment,
		user: localStorage.getItem("username"),
		postID: id,
	});
	setComment("");
};
```

Create a listener to the event on the server that adds the comment to the list of comments.

```jsx
socket.on("newComment", (data) => {
	const { postID, user, comment } = data;

//👇🏻 filters the notion post via its ID
let result = notionPosts.filter((post) => post.id === postID);

//👇🏻 Adds the comment to the comments list
	result[0].comments.unshift({
		id: fetchID(),
		user,
		message: comment,
	});
//👇🏻 sends the updated details to the React app
	socket.emit("postDetails", result[0]);
});
```

Update the `NotionPost.js` file to display any existing comments.

```jsx
return (
	<div className='notionPost'>
		<div className='notionPost__container'>
			<h1>{post.title}</h1>
			<div className='notionPost__meta'>
				<p className='notionPost__author'>By {post.author}</p>
				<p className='notionPost__date'>Created on {post.createdAt}</p>
			</div>

			<div className='notionPost__content'>{post.content}</div>
		</div>

		<div className='comments__container'>
			<h2>Add Comments</h2>
			<form className='comments__inputContainer' onSubmit={handleAddComment}>
				<textarea
					placeholder='Type in your comments...'
					rows={5}
					className='comments__input'
					value={comment}
					required
					onChange={(e) => setComment(e.target.value)}
				/>
				<button className='comments__cta'>Add Comment</button>
			</form>

			{/** Displays existing comments to the user */}
			<div>
				{post.comments.map((item) => (
					<p className='comment' key={item.id}>
						<span style={{ fontWeight: "bold", marginRight: "15px" }}>
							{item.user}
						</span>
						{item.message}
					</p>
				))}
			</div>
		</div>
	</div>
);
```

Congratulations!🎊 You can now create posts and add comments with Socket.io. For the remaining part of this tutorial, I'll guide you through sending notifications to every user you tag in your post using Novu.

## How to add Novu to a React and Node.js application

Novu allows you to add various notification types, such as email, SMS, and in-app notifications. In this tutorial, you will learn how to create a Novu project, add Novu to your React and Node.js projects, and send an in-app notification with Novu.

Install the Novu Node.js SDK on the server and the Notification Center in the React app.

```bash
👇🏻 Install on the client
npm install @novu/notification-center

👇🏻 Install on the server
npm install @novu/node
```

Create a Novu project by running the code below. A personalised dashboard is available to you.

```bash
👇🏻 Run on the client
npx novu init
```

You will need to sign in with Github before creating a Novu project. The code snippet below contains the steps you should follow after running `npx novu init`

```bash
Now let's setup your account and send your first notification
❓ What is your application name? Notionging-Platform
❓ Now lets setup your environment. How would you like to proceed?
   > Create a free cloud account (Recommended)
❓ Create your account with:
   > Sign-in with GitHub
❓ I accept the Terms and Condidtions (https://novu.co/terms) and have read the Privacy Policy (https://novu.co/privacy)
    > Yes
✔️ Create your account successfully.

We've created a demo web page for you to see novu notifications in action.
Visit: http://localhost:57807/demo to continue
```

Visit the demo web page `http://localhost:57807/demo`, copy your subscriber ID from the page, and click the Skip Tutorial button. We'll be using it later in this tutorial.


![Demo Paaa](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/9dloixzqj5pe1c07r0ur.png)


Congratulations!🎊 You’ve successfully added Novu to your React and Node.js project. Next, let’s learn how to add in-app notifications to the notionging application to notify users when we tag them to a post.

### Adding in-app notifications with Novu

Create a `Notify.js` file within the `src/components` folder and copy the code below into the file. It contains the elements required for in-app notifications from the [documentation](https://docs.novu.co/notification-center/react-components).

```jsx
import React from "react";
import {
	NovuProvider,
	PopoverNotificationCenter,
	NotificationBell,
} from "@novu/notification-center";
import { useNavigate } from "react-router-dom";

const Notify = () => {
	const navigate = useNavigate();

	const onNotificationClick = (notification) =>
		navigate(notification.cta.data.url);

	return (
		<div>
			<NovuProvider
				subscriberId='<YOUR_SUBSCRIBER_ID>'
				applicationIdentifier='<YOUR_APP_ID>'
			>
				<PopoverNotificationCenter
					onNotificationClick={onNotificationClick}
					colorScheme='light'
				>
					{({ unseenCount }) => <NotificationBell unseenCount={unseenCount} />}
				</PopoverNotificationCenter>
			</NovuProvider>
		</div>
	);
};

export default Notify;
```

The code snippet above adds Novu notification bell icon to the Notify component, enabling us to view all the notifications within the application.

> The `NovuProvider` component requires your Subscriber ID - copied earlier from  `http://localhost:57807/demo` and your application ID available in the Settings section under API Keys on the [Novu Manage Platform](https://web.novu.co/settings).


![Novu Provider](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/m21fn2ugwwdimu6209c3.jpeg)


Import the Notify component into the `Home.js` file and display the bell icon as below:


![Notify](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/0uwlaagobg3gj7lxoedl.jpeg)


```jsx
return (
		<div className='home'>
			<nav className='home__navbar'>
				<h2>HackNotion</h2>
				<div className='home__buttons'>
					<button className='home__createBtn' onClick={createPostBtn}>
						CREATE POST
					</button>
					<Notify />
				</div>
			</nav>
	</div>
)
```

Next, create the workflow for the application, which describes the features you want to add to the application.

Select Notification from the Development sidebar and create a notification template. Click the newly created template, then, Workflow Editor, and ensure the workflow is as below:

![Notification](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/e3ul5arrff4as4p6txhq.gif)

From the image above, Novu triggers the Digest engine before sending the in-app notification.

> [Novu Digest](https://docs.novu.co/platform/digest) allows us to control how we want to send notifications within the application. It collects multiple trigger events and sends them as a single message. The image above sends notifications every 2 minutes, and it can be effective when you have many users and frequent updates.
> 

Click the `In-App`step from the image above and edit the notification template to contain the content below.

```jsx
{{sender}} tagged  you to a post
```

> Novu allows you to add dynamic content or data to the templates using [the Handlebars templating engine](https://docs.novu.co/platform/templates#messages). The data for the `sender` variable will be inserted into the template as a payload from the request within our app.

Save the template by clicking `Update` button and head back to your code editor.

## Sending notifications with Novu

Since we want to send notifications to users when we tag them to a post, we will have to store each username on the server, show them on the suggestion list provided by React Tags, and send them notifications via Novu.

Update the `handleLogin` function within the `Login.js` file to send the username to the server when they sign in.

```jsx
const handleLogin = (e) => {
	e.preventDefault();
	//👇🏻 sends the username to the server
	socket.emit("addUser", username);
	localStorage.setItem("username", username);
	navigate("/dashboard");
};
```

Listen to the event and store the username in an array on the server.

```jsx
let allUsers = [];

socket.on("addUser", (user) => {
	allUsers.push(user);
});
```

Also, render the list of users via another route on the server.

```jsx
app.get("/users", (req, res) => {
	res.json(allUsers);
});
```

**To show the users within the React Tags suggestion list, you need to send a request to the API route, get the list of users, and pass them into the list.**
Update the `CreatePost` function to fetch the list of users, and save them within the local storage before navigating the `post/create` route.

```jsx
const createPostBtn = () => {
	fetchUser();
	navigate("/post/create");
};

const fetchUser = () => {
	fetch("http://localhost:4000/users")
		.then((res) => res.json())
		.then((data) => {
			//👇🏻 converts the array to a string
			const stringData = data.toString();
			//👇🏻 saved the data to local storage
			localStorage.setItem("users", stringData);
		})
		.catch((err) => console.error(err));
};
```

Next, retrieve all the users from the local storage and pass them into the suggestion list provided by React Tags for display within the `CreatePost` component.

```jsx
const [users, setUsers] = useState([]);

useEffect(() => {
	function getUsers() {
		const storedUsers = localStorage.getItem("users").split(",");
		setUsers(storedUsers);
	}
	getUsers();
}, []);

const suggestions = users.map((name) => {
	return {
		id: name,
		text: name,
	};
});
```


![Notify](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/jand17uke2qwb48iggxr.gif)

**To notify each tagged user, create a function that loops through the users on the server and sends them a notification via Novu to them.**

Import and initiate Novu on the server.

```jsx
const { Novu } = require("@novu/node");
const novu = new Novu("<YOUR_API_KEY>")
```

Update the `createPost` listener on the backend to send a notification to all tagged users.

```jsx
//👇🏻 Loops through the tagged users and sends a notification to each one of them
const sendUsersNotification = (users, sender) => {
	users.forEach(function (user) {
		novuNotify(user, sender);
	});
};

//👇🏻 sends a notification via Novu
const novuNotify = async (user, sender) => {
	try {
		await novu
			.trigger("<TEMPLATE_ID>", {
				to: {
					subscriberId: user.id,
					firstName: user.text,
				},
				payload: {
					sender: sender,
				},
			})
			.then((res) => console.log("Response >>", res));
	} catch (err) {
		console.error("Error >>>>", { err });
	}
};

socket.on("createPost", (data) => {
	const { postTitle, postContent, username, timestamp, tags } = data;
	notionPosts.unshift({
		id: fetchID(),
		title: postTitle,
		author: username,
		createdAt: timestamp,
		content: postContent,
		comments: [],
	});
	//👇🏻 Calls the function to send a notification to all tagged users
	sendUsersNotification(tags, username);

	socket.emit("updatePosts", notionPosts);
});
```

Congratulations! 💃🏻 We've completed the code for this project.


![Congratulations](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/8vlaw6lq2njmob0s25ps.png)

## Conclusion

So far, you've learned how to set up Socket.io in a React and Node.js application, send messages between the client and a Node.js server, add Novu to a React and Node.js application, and send notifications with Novu.

This tutorial demonstrates what you can build using Socket.io and Novu. Feel free to improve on the project by adding an authentication library and saving the blog posts to a database that supports real-time communication.

The complete code for this tutorial is available here: [https://github.com/novuhq/blog/tree/main/blogging-platform-with-react-socketIO](https://github.com/novuhq/blog/tree/main/blogging-platform-with-react-socketIO)
Thank you for reading!


**P.S** I would be super grateful if you can help us out by starring the library 🤩
[https://github.com/novuhq/novu](https://github.com/novuhq/novu)

[![GitHub](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/imvcgndr0j0138n89fzw.png)](https://github.com/novuhq/novu)