How would I see if a specific item is on a list in JavaScript?

Question

I have a list called usernames, that stores usernames. I want to see if the specific username is on the list and deny the person if it is. Code:

var usernames = ["someuser",""];

io.on('connection', function(socket){

  socket.on("join", function(room, username == usernames){
    if (username != "" || username == usernames){
   // do something
    }
  })

Answer 1

Just use Array.prototype.includes:

usernames.includes(username)