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.

var spans = line.markedSpans;
    if (!spans) return;
    for (var i = 0; i < spans.length; ++i)
      spans[i].marker.detachLine(line);
    line.markedSpans = null;
  }
  function attachMarkedSpans(line, spans) {
    if (!spans) return;
    for (var i = 0; i < spans.length; ++i)
      spans[i].marker.attachLine(line);
    line.markedSpans = spans;
  }
  
  var LineWidget = CodeMirror.LineWidget = function(cm, node, options) {
    if (options) for (var opt in options) if (options.hasOwnProperty(opt))
      this[opt] = options[opt];
    this.cm = cm;
    this.node = node;
  };
  eventMixin(LineWidget);
  function widgetOperation(f) {