How to implement a simple chat application using JavaScript-Front-end Q&A-php.cn

How to implement a simple chat application using JavaScript

PHPz

Release： 2023-04-18 18:27:47

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In recent years, with the continuous development of Internet technology, instant messaging has become an indispensable part of people's daily lives. Nowadays, chat tools have become one of the important ways for people to communicate. This article will introduce how to implement a simple chat application using JavaScript.

1. Basic knowledge

Before starting to implement a chat application, you need to master some basic front-end development knowledge, such as HTML, CSS and JavaScript. If you haven't mastered these techniques yet, learn their basics first.

2. Interface design of chat application

Before implementing the chat application, you need to design a simple interface first. In this application, we will use HTML and CSS to create web page layouts and JavaScript to interact with the user.

First, we need to create an HTML file, and then add a text box and a send button to the page:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>简易聊天应用</title>
  <link rel="stylesheet" href="style.css">
</head>
<body>
  <div id="chat-log"></div>
  <input id="chat-input" type="text" placeholder="请输入一些文字...">
  <button id="send-button">发送</button>
  
  <script src="app.js"></script>
</body>
</html>

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Next, set the style of the page in the CSS file:

body {
  font-family: Arial, sans-serif;
  background-color: #f0f0f0;
  margin: 0;
  padding: 0;
}

#chat-log {
  background-color: #ffffff;
  height: 400px;
  max-width: 600px;
  margin: 20px auto;
  overflow: scroll;
  padding: 10px;
}

#chat-input {
  width: 100%;
  height: 40px;
  box-sizing: border-box;
  padding: 10px;
  font-size: 16px;
  border: 2px solid #cccccc;
}

#send-button {
  display: block;
  margin: 20px auto;
  border: none;
  background-color: #4285f4;
  color: #ffffff;
  font-size: 16px;
  padding: 10px 20px;
  cursor: pointer;
}

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Finally, in order to make the chat application interactive, we need to write JavaScript code. The following sections will guide you on how to create a simple chat application using JavaScript.

3. Use JavaScript to implement chat applications

1. Create WebSockets

WebSockets is a new type of two-way communication technology between the client and the server. Using it, we can create a real-time chat application.

In our application, we need to create a WebSocket so that the client can communicate with the server. If you don't know WebSocket yet, learn its basics first.

The following is the JavaScript code for how to create WebSocket:

const socket = new WebSocket('ws://localhost:3000');

socket.addEventListener('open', function (event) {
  console.log('服务器已连接');
});

socket.addEventListener('message', function (event) {
  console.log('服务器发送了一条消息: ', event.data);
});

socket.addEventListener('close', function (event) {
  console.log('服务器已关闭');
});

socket.addEventListener('error', function (event) {
  console.log('服务器发生了错误');
});

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In the above code, we use the WebSocket API to create a WebSocket instance. The parameter we pass is the address of the server, so please modify the parameters here according to your actual server address.

After creating the WebSocket, we need to bind the open, message, close and error events to it. These events represent a successful connection to the server, a message received, a connection closed, and an error.

2. Sending and receiving messages

When implementing a chat application, we need to write code to send messages entered by users to the server and receive messages sent by other users.

The operation of sending a message is very simple. You only need to get the value in the text box on the page when the user clicks the "Send" button, and send it to the server through WebSocket.

const inputElement = document.querySelector('#chat-input');
const sendButtonElement = document.querySelector('#send-button');

sendButtonElement.addEventListener('click', function(event) {
  event.preventDefault();

  const message = inputElement.value;
  inputElement.value = '';

  socket.send(message);
});

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The above code creates an event listener. When the user clicks the "Send" button, it gets the value in the text box and sends it to the server through WebSocket. To make the code more robust, we will also add a click event to the "sendButtonElement" element.

Next, we need to write code to receive messages sent by other users. Implementing this feature can make your chat application more useful. When a message is received, we need to update the chat history on the page so that the user sees the message.

const chatLogElement = document.querySelector('#chat-log');

socket.addEventListener('message', function(event) {
  const message = event.data;

  const chatMessageElement = document.createElement('div');
  chatMessageElement.innerText = message;

  chatLogElement.appendChild(chatMessageElement);
});

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In the above code, we use the addEventListener method to bind the message event for WebSocket. When the server sends a message, we first splice the data into a text message, then create a div element and add the message to it.

3. Test the chat application

Now, our chat application is basically completed. To test, you can start a Node.js server on your local machine and open your chat app page in a browser.

Enter the following command in the terminal to start the Node.js server:

node app.js

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Among them, app.js is the file name of the server code we wrote. If you haven't written this code yet, please first refer to the tutorial on how to implement WebSockets using Node.js.

Now you can open the chat page in your browser and enter a message in the text box. Then, click the "Send" button. At this point, you should see the message you entered in your chat history.

# 4. Summary

JavaScript is a powerful programming language that can be used to write very practical chat applications. In this article, we introduced how to implement a simple chat application using WebSocket. We created a page using HTML, CSS, and JavaScript, and implemented real-time communication using WebSocket. If you haven't mastered these skills yet, I suggest you first master these basics before doing this small project. ###

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