index.js

const express = require("express");
const bodyParser = require("body-parser");

const app = express();
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());

let clientId = 0;
let clients = {};
let actUserName = "";
let clientNames = {};

let sendText = (text, showUserName = true) => {
  for (clientId in clients) {
    let data = "";
    let date = new Date();
    let timestamp = `[${date.getHours()}:${date.getMinutes()}]`;
    if (showUserName) {
      data = `data: ${timestamp} <${actUserName}> ${text}\n\n`;
    } else {
      data = `data: ${timestamp} ${text}\n\n`;
    }
    clients[clientId].write(data);
  }
};

app.use("/", express.static("static"));

app.get("/chat/:name", (req, res) => {
  res.writeHead(200, {
    "Content-Type": "text/event-stream",
    "Cache-Control": "no-cache",
    Connection: "keep-alive"
  });
  res.write("\n");
  (function(clientId) {
    clients[clientId] = res;
    clientNames[clientId] = req.params.name;
    req.on("close", () => {
      delete clients[clientId];
      actUserName = "";
      sendText(clientNames[clientId] + " disconnected!", false);
      delete clientNames[clientId];
    });
  })(++clientId);

  sendText(req.params.name + " connected!", false);
  let allMates = "";
  for (cliId in clientNames) {
    allMates += `${clientNames[cliId]}`;
    if (cliId < clientId) allMates += " ";
  }
  sendText(`logged in [${allMates}]`, false);
});

app.post("/write/", (req, res) => {
  actUserName = req.body.name;
  sendText(req.body.text);
  res.json({ success: true });
});

app.listen(3000, () => {
  console.log("Server running.");
});