Socket.io and Async Not Returning Values

Question

I have a async client function that returns whether or not a username is taken. I am using socket.io for sending packets of data, and I am having trouble finding out what the issue is.

This is the function (Browser):

let socket = io();
async function createAccount(username, password){
    socket.emit('create account', {username:username, password:password});

    let res;

    await socket.on('create account return', (data) => {
        res = data.failed;
    });
    return res;
};

Here is my test script, which should log true if the username is valid, and false otherwise:

createAccount('bagel03', '12345').then((val)=>console.log(val));

Instead, I always get undefined, but if I change the return statement in the createAccount function to:

return true;

It works and logs true.

I am new to async await (this is my first project with it), and nothing online has been helping. What is the problem?

EDIT: Here is the server code (Node.js):

const io = require('socket.io')(server,{ pingTimeout: 4000, pingInterval: 4000 })

io.sockets.on('connect',  socket =>{
    //account stuff
    socket.on('create account',  data =>{
        if(!isUsernameTaken(data.username)){
            id = addAccount(data);
            socket.emit('create account return',{failed:false})
        }else socket.emit('create account return', {failed:true})

    });
});

Answer 1

You can't use await on an even listener. If you want to write your createAccount in order to be called with await you just need to make it to return a Promise. Something like:

let socket = io();
function createAccount(username, password) {
  return new Promise((resolve, reject) => {
    socket.emit('create account', {username:username, password:password});

    socket.once('create account return', (data) => resolve(data.failed));
  });
};