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 flattenSpans = mode.flattenSpans;
    if (flattenSpans == null) flattenSpans = cm.options.flattenSpans;
    var curStart = 0, curStyle = null;
    var stream = new StringStream(text, cm.options.tabSize), style;
    if (text == "" && mode.blankLine) mode.blankLine(state);
    while (!stream.eol()) {
      if (stream.pos > cm.options.maxHighlightLength) {
        flattenSpans = false;
        if (forceToEnd) processLine(cm, text, state, stream.pos);
        stream.pos = text.length;
        style = null;
      } else {
        style = mode.token(stream, state);
      }
      if (!flattenSpans || curStyle != style) {
        if (curStart < stream.start) f(stream.start, curStyle);
        curStart = stream.start; curStyle = style;
      }
      stream.start = stream.pos;
    }
    while (curStart < stream.pos) {
      
      var pos = Math.min(stream.pos, curStart + 50000);
      f(pos, curStyle);
      curStart = pos;
    }
  }
  function highlightLine(cm, line, state, forceToEnd) {