Right now we use codemirror's JavaScript mode on the website but there's a JSX mode now so we should start using that instead.

counter = Infinity;
      e_preventDefault(e);
      focusInput(cm);
      off(document, "mousemove", move);
      off(document, "mouseup", up);
    }
    var move = operation(cm, function(e) {
      if (!ie && !e_button(e)) done(e);
      else extend(e);
    });
    var up = operation(cm, done);
    on(document, "mousemove", move);
    on(document, "mouseup", up);
  }
  function gutterEvent(cm, e, type, prevent, signalfn) {