Trying to start a Websocket

I'm trying to start a websocket server through the ESP8266 but keep receiving an error saying that Constructor should be a function and not undefined. This is my code after connecting the ESP to wifi. What is going wrong here? I have node and ws installed through terminal.

var WebSocketServer = require('ws').Server,
wss = new WebSocketServer({port:8080});

wss.on('connection', function (wss) {
wss.on('message', function (message) {

console.log('received: %s', message);

});

setInterval(

() => ws.send(`${new Date()}`),
1000

);
});