proxy.js

// wrap "old" sunbeam instance so usage stays same for users

class Sbw {
  constructor(client, opts) {
    const w = new Sunbeam({}, opts)

    const trap = {
      get: function(obj, prop) {
        if (obj[prop]) return obj[prop]
   
        if (/^on.*/.test(prop)) {
          const hook = obj.msgHandler.addCallback(prop)
          
          // cache
          obj[prop] = hook
          return hook
        }
      }
    }

    var ws = new Proxy(w, trap);

    return ws
  }
}

const ws = new Sbw({}, opts)

ws.on('open', () => {
  ws.onOrderBook({ symbol: 'EOS.USD' }, (ob) => {
    console.log('ws.onOrderBook({ symbol: "EOS.USD" }')
    console.log(ob)
  })
  ws.subscribeOrderBook('EOS.USD')
})

ws.open()

q_msgHandler.js

class MsgHandler extends EventEmitter {
  constructor (opts) {
    super()

    this.conf = conf

    this._channels = {}
    
    this.conf.transports.pub.on('message', this.handleMessage.bind(this))
    
    this.handlers = {}
  }

  addCallback (name) {
    const hook = (filter, handler) => {
      let mod = 'def'

      if (filter && filter.symbol) {
        mod = filter.symbol
      }

      const [handlerNamePlain] = this.getHandlerNames(name, mod)
      console.log("setting hook", handlerNamePlain)
      this.handlers[handlerNamePlain] = handler
    }

    return hook
  }

  getHandlerNames (name, mod) {
    if (/^on/.test(name)) {
      const plain = name + '#' + mod
      const managed = name + '#' + mod

      return [plain, managed]
    }

    const plain = 'on' + name + '#' + mod
    const managed = 'onManaged' + name + '#' + mod

    return [plain, managed]
  }

  handleMessage (msg) {
    if (Array.isArray(msg)) {
      const [ chanId, data ] = msg

      this.handleOrderbookMessage(chanId, data, msg)
    }
  }

  handleOrderbookMessage (chanId, data, msg) {
    if (!this._channels['book'][chanId]) {
      return
    }

    const { symbol } = this._channels['book'][chanId]

    const [pcb, mcb] = this.getHandlerNames('OrderBook', symbol)
    if (this.handlers[pcb]) {
      this.handlers[pcb](data)
    }
  }