使用箭头函数重构嵌套函数

Question

I have trouble in refactoring the following code block into separate functions.

socketHandler = (io) => {
  io.on('connection', (socket) => {
    socket.on('doLogin', data => {
      userService.getUserByName(data.uname)
        .then((doc) =>{
          if(doc && doc.pwd===data.pwd){
            socket.emit('onLogin', {status:'SUCCESS'});
          }
        }, (error) => {
          socket.emit('onLogin', {status:'Error in the application'});
        });
    });
  });
}

app.configure(socketio(socketHandler));

I tried refactoring the above code as follows.

doLogin = data => {
  userService.getUserByName(data.uname)
    .then((doc) =>{
      if(doc && doc.pwd===data.pwd){
        socket.emit('onLogin', {status:'SUCCESS'});
      }
    }, (error) => {
      socket.emit('onLogin', {status:'Error in the application'});
    });
}

socketHandler = (io) => {
  io.on('connection', (socket) => {
    socket.on('doLogin', doLogin);
  });
}

app.configure(socketio(socketHandler));

I am getting a run-time error as socket is not defined.

How to get reference to 'socket' in the function 'doLogin'?

I also tried the following way and could not make it work.

doLogin = socket => data => {

Also tried as follows

socket.on('doLogin', doLogin.bind(socket));

Need some help in fixing this.

Thanks.

Answer 1

After you broke up the functions you lost reference to socket object. You could try, in SocketHandler

socket.on('doLogin', (data) => doLogin(data, socket));

and redefine doLogin as

doLogin = (data, socket) => {

Answer 2

doLogin.bind(socket) won't work if doLogin is arrow function, because arrow functions cannot be bound. Instead, it should be a regular function:

function doLogin(data) {
  const socket = this;
  ...
}
...
socket.on('doLogin', doLogin.bind(socket));