【发布时间】：2021-06-07 23:44:33
【问题描述】：
我正在尝试通过此链接创建一个聊天应用程序：https://socket.io/get-started/chat 具有能够在聊天中发送和显示图像的附加功能，但我之前所能做的就是上传图像。目前，我正在尝试使用存储的图像发送到聊天室，但无法这样做。
index.html
<!DOCTYPE html>
<html>
<head>
<title>Socket.IO chat</title>
<style>
body { margin: 0; padding-bottom: 3rem; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif; }
#form { background: rgba(0, 0, 0, 0.15); padding: 0.25rem; position: fixed; bottom: 0; left: 0; right: 0; display: flex; height: 3rem; box-sizing: border-box; backdrop-filter: blur(10px); }
#input { border: none; padding: 0 1rem; flex-grow: 1; border-radius: 2rem; margin: 0.25rem; }
#input:focus { outline: none; }
#form > button { background: #333; border: none; padding: 0 1rem; margin: 0.25rem; border-radius: 3px; outline: none; color: #fff; }
#messages { list-style-type: none; margin: 0; padding: 0; }
#messages > li { padding: 0.5rem 1rem; }
#messages > li:nth-child(odd) { background: #efefef; }
</style>
</head>
<body>
<ul id="messages"></ul>
<form id="form" action="">
<input id="input" autocomplete="off" /><button>Send</button>
<input type="file" id="upload-btn" name="filename"><input type="submit">
</form>
<script src="/socket.io/socket.io.js"></script>
<script>
var socket = io();
var messages = document.getElementById('messages');
var form = document.getElementById('form');
var input = document.getElementById('input');
form.addEventListener('submit', function(e) {
e.preventDefault();
if (input.value) {
socket.emit('chat message', input.value);
input.value = '';
}
});
socket.on('chat message', function(msg) {
var item = document.createElement('li');
item.textContent = msg;
messages.appendChild(item);
window.scrollTo(0, document.body.scrollHeight);
});
var ctx = document.getElementById('upload-btn').getContext('2d');
// ...
socket.on("image", function(info) {
if (info.image) {
var item = document.createElement('li');
var img = new Image();
messages.appendChild(item);
window.scrollTo(0, document.body.scrollHeight);
img.src = 'data:image/png;base64,' + info.buffer;
ctx.drawImage(img, 0, 0);
}
});
</script>
</body>
</html>
index.js
var express = require('express');
var path = require('path');
var app = express();
app.use(express.static(path.join(__dirname, 'public')));
const http = require('http').Server(app);
const io = require('socket.io')(http);
const fs = require('fs'); // required for file serving
app.get('/', (req, res) => {
res.sendFile(__dirname + '/index.html');
});
io.on('connection', (socket) => {
console.log('a user connected');
socket.on('disconnect', () => {
console.log('user disconnected');
});
});
io.on('connection', (socket) => {
socket.on('chat message', (msg) => {
console.log('message: ' + msg);
});
});
http.listen(3000, () => {
console.log('listening on *:3000');
});
io.emit('some event', { someProperty: 'some value', otherProperty: 'other value' }); // This will emit the event to all connected sockets
io.on('connection', (socket) => {
socket.broadcast.emit('hi');
});
io.on('connection', (socket) => {
socket.on('chat message', (msg) => {
io.emit('chat message', msg);
});
});
io.on('connection', function(socket){
fs.readFile(__dirname + '/images/image.jpg', function(err, buf){
// it's possible to embed binary data
// within arbitrarily-complex objects
socket.emit('image', { image: true, buffer: buf.toString('base64') });
console.log('image file is initialized');
});
});
【问题讨论】：
-
@ggorlen 我已经尝试过了，但它没有将图像上传到聊天中。也许这是一个 html 错误？
-
document.getElementById('upload-btn').getContext('2d');没有意义——#upload-btn是一个按钮。这段代码应该在控制台中给您一个错误，解释问题，即getContext不是一个函数。尝试使用画布而不是按钮来调用getContext("2d")。可能还有其他错误；最好具体说明您的特定问题/错误是什么。 -
@ggorlen 好吧抱歉没有具体说明。
标签： javascript html node.js sockets socket.io