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.

if (cm.options.lineWrapping) {
      cm.display.wrapper.className += " CodeMirror-wrap";
      cm.display.sizer.style.minWidth = "";
    } else {
      cm.display.wrapper.className = cm.display.wrapper.className.replace(" CodeMirror-wrap", "");
      computeMaxLength(cm);
    }
    estimateLineHeights(cm);
    regChange(cm);
    clearCaches(cm);
    setTimeout(function(){updateScrollbars(cm);}, 100);
  }
  function estimateHeight(cm) {
    var th = textHeight(cm.display), wrapping = cm.options.lineWrapping;
    var perLine = wrapping && Math.max(5, cm.display.scroller.clientWidth / charWidth(cm.display) - 3);
    return function(line) {
      if (lineIsHidden(cm.doc, line))
        return 0;
      else if (wrapping)
        return (Math.ceil(line.text.length / perLine) || 1) * th;
      else
        return th;
    };
  }
  function estimateLineHeights(cm) {