调用在回调中定义的函数

Question

I am having a difficulty understanding Javascript-style function definitions.

I have a Websocket server:

var WebSocketServer = require('ws').Server,
wss = new WebSocketServer();

wss.on('connection', function (ws) {
  ws.on('message', function (message) {
    console.log('received: %s from client', message);
  })
  ws.send('hello client');
})

And I want to send a message to the connected clients when another function importantEvent() is called.

function importantEvent(message) {
  //send message to the connected client
  ws.send('hello client');
}

What is the good way of calling ws.send() inside importantEvent() ?

Answer 1

I use EventEmitter to similar things to avoid a strong module strength.

// eventManager.js
const EventEmitter = require('events');
class EventManager extends EventEmitter {}
const eventManager = new EventManager();

module.exports = eventManager;

// websocket.js
var eventManager = require('eventManager');
var WebSocketServer = require('ws').Server,
wss = new WebSocketServer();

wss.on('connection', function (ws) {
...
})

function broadcast(data, filter) {
    wss.clients.forEach( ... // depends on library using to web-socket
}

eventManager.on('my-event', function (arg1, arg2) {
    broadcast({arg1, arg2})
});

// in any other files
var eventManager = require('eventManager');

eventManager.emit('my-event', 'hello', 'world');

Answer 2

It's a matter of what clients you want to reach. In wss.on('connection'... event, the ws received by the function is the client that is connecting to the server in this event.

As you want send a message to all the clients connected, you need to use the broadcast method

var WebSocketServer = require('ws').Server,
wss = new WebSocketServer();

function importantEvent(message) {
    // Broadcast to all.
    wss.broadcast = function broadcast(data) {
    wss.clients.forEach(function each(client) {
      if (client.readyState === WebSocket.OPEN) {
        client.send('hello client');
      }
    });
  };
}