We Shall See

function makeid() {
  var id = "";
  // uri_unreserved per http://www.ietf.org/rfc/rfc3986.txt
  var uri_unreserved = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.~";

  for (var i = 0; i < 5; i++)
    id += uri_unreserved.charAt(Math.floor(Math.random() * uri_unreserved.length));

  return id;
}

console.log(makeid());