WEB game logic example

example.js

// List with users that have set a username
let activePlayers = [];
// username of player that is currently drawing
let playerDrawing;

let word;

// This will execute everytime a new player connects
io.sockets.on('connection', function(socket) {
  // username is not yet defined
  let username;

  // let the client know that a username is required (this can be left out)
  socket.emit('require-username');

  // this will execute as soon as the user has set a username
  socket.on('receive-username', function(name) {
    // the name will be stored in the local variable
    username = name;

    // the client will be notified that the user has been set to active
    socket.emit('player-active');
    // the user is added to the array of active players
    activePlayers.push(name);
  });

  // this is called when a user sends a message
  socket.on('chat', function(message) {
    // broadcast the message to all other users
    socket.broadcast.emit('chat', message);

    // check if word equals the content of the message and it's not sent by the player drawing
    if (message === word && playerDrawing !== username) {
      // if yes round is finished and the username of the winning user is send to everybody
      io.sockets.emit('round-finished', username);

      // reset variables
      playerDrawing = null;
      word = null;

      // TODO: adjust highscores
    }
  })

  // this is called by the drawing user after he gets selected
  socket.on('request-word', function() {
    // the user receives his wordlist but only if he is really the one drawing
    if (username === playerDrawing) {
      socket.emit(word);
    }
  })

  // this will execute when the client loses connection (closer browser tab, switches to another site, etc.)
  // and must not be called manually! 
  socket.on('disconnect', function() {
    // find the user in the array
    let user = activePlayers.findIndex(item => item === username);
    // if he was found remove him from the array
    if (user >= 0) {
      activePlayers.splice(user, 1);
    }
  })
})

// this function recursively calls itself and checks if someone is drawing at the moment
function checkIfSomeoneIsDrawing() {
  setTimeout(function() {
    // Only if more than 2 players are active and noone is drawing a round can be started
    if (activePlayers.length >= 2 && !playerDrawing) {
      // select a random player to start drawing
      let randomNumber = Math.random();
      randomNumber = randomNumber * activePlayers.length - 1;
      playerDrawing = activePlayers[Math.round(randomNumber)];

      /* TODO: set word variable from wordlist */

      // Let everyone know who is drawing
      io.sockets.emit('start-drawing', playerDrawing);
    }

    // function is calls itself infinitely
    checkIfSomeoneIsDrawing();
  }, 1000)
}

checkIfSomeoneIsDrawing();