exponentialBackoff.js

var attempts = 1;

function createWebSocket () {
  var connection = new WebSocket();
  
  connection.onopen = function () {
    // reset the tries back to 1 since we have a new connection opened.
    attempts = 1; 

    // ...Your app's logic...
  }
 
  connection.onclose = function () {
    var time = generateInterval(attempts);
    
    setTimeout(function () {
        // We've tried to reconnect so increment the attempts by 1
        attempts++;
        
        // Connection has closed so try to reconnect every 10 seconds.
        createWebSocket(); 
    }, time);
  }
}

function generateInteval (k) {
  var maxInterval = (Math.pow(2, k) - 1) * 1000;
  
  if (maxInterval > 30*1000) {
    maxInterval = 30*1000; // If the generated interval is more than 30 seconds, truncate it down to 30 seconds.
  }
  
  // generate the interval to a random number between 0 and the maxInterval determined from above
  return Math.random() * maxInterval; 
}

Reconnection will happen only once, use setInterval instead setTimeout

@ds0nt
Your one-line code lack a random number generate process.