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The EventSource's message object not have a retry property bug
The EventSource's message object not have a retry property bug
server.js
import fs from 'node:fs';
import express from 'express';
const app = express();
app.use(express.static('public'));
const convertImageToBase64URL = (filename, imageType = 'png') => {
try {
const buffer = fs.readFileSync(filename);
// const base64String = Buffer.from(buffer, 'base64');
const base64String = Buffer.from(buffer).toString('base64');
// console.log(`base64String`, base64String.slice(0, 100));
return `data:image/${imageType};base64,${base64String}`;
} catch (error) {
throw new Error(`file ${filename} no exist ❌`)
}
}
app.get('/sse', (req, res) => {
res.writeHead(200, {
// 'Content-Type': 'text/event-stream',
'Content-Type': 'text/event-stream; charset=utf-8',
'Cache-Control': 'no-cache',
'Connection': 'keep-alive',
'Access-Control-Allow-Origin': "*",
});
let i = 0;
let uid = setInterval(() => {
console.log(`i`, i);
if(i < 10) {
i++;
const data = convertImageToBase64URL("./public/test.png");
console.log(`SSE ${i}`, data.slice(0, 100));
// event id `lastEventId` ✅
const id = 2023;
// ms
const retryTimes = 1000 * 60;
res.write(`id: ${id}\n`);
res.write(`retry: ${retryTimes}\n`);
// custom event type `custom_message`\n ✅
res.write(`event: custom_event_message\n`);
res.write(`data: ${data}\n\n`);
} else {
clearInterval(uid);
}
}, 3000);
});
// http://localhost:3000/sse
const port = 3000;
app.listen(port, () => {
console.log(`SSE server is running on: http://localhost:${port}/`);
});
client.js
window.addEventListener(`load`, (e) => {
console.log(`page loaded ✅`);
if (!!window.EventSource) {
const img = document.querySelector(`#sse`);
const source = new EventSource('http://localhost:3000/sse');
source.onopen = (event) => {
console.log(`✅ Connection to server opened.`, event);
};
source.addEventListener(`custom_event_message`, (event) => {
console.log(`\nevent`, event);
const timestamp = event.timeStamp;
console.log(`event.timeStamp`, timestamp);
const retry = event.retry;
console.log(`event.retry`, retry);
// undefined ❌
const id = event.lastEventId;
console.log(`event.lastEventId`, id);
const type = event.type;
console.log(`event.type`, type);
const data = event.data;
// console.log(`🚀 event.data =`, data);
img.src = `${data}`;
});
source.onerror = (err) => {
console.log(`❌ EventSource failed.`, err);
// setTimeout(() => {
// console.log(`⚠️ After 3 seconds, auto close connection!`);
// source.close();
// }, 3000);
};
} else {
console.log(`Your browser doesn't support SSE ❌`);
}
});
refs
https://javascript.info/server-sent-events#server-response-format
https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#retry