The :display is a keyword, which works like keywords in Ruby or Erlang; it's a special, never-garbage-collected string for when you use the same string over and

The :display is a keyword, which works like keywords in Ruby or Erlang; it's a special, never-garbage-collected string for when you use the same string over and over. Though I'm not sure whether the implementation is the same when compiling to Javascript instead of the JVM.