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.

cm.doc.mode = CodeMirror.getMode(cm.options, cm.doc.modeOption);
    cm.doc.iter(function(line) {
      if (line.stateAfter) line.stateAfter = null;
      if (line.styles) line.styles = null;
    });
    cm.doc.frontier = cm.doc.first;
    startWorker(cm, 100);
    cm.state.modeGen++;
    if (cm.curOp) regChange(cm);
  }
  function wrappingChanged(cm) {