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.display.measureLineCache.length = cm.display.measureLineCachePos = 0;
    cm.display.cachedCharWidth = cm.display.cachedTextHeight = null;
    if (!cm.options.lineWrapping) cm.display.maxLineChanged = true;
    cm.display.lineNumChars = null;
  }
  function pageScrollX() { return window.pageXOffset || (document.documentElement || document.body).scrollLeft; }
  function pageScrollY() { return window.pageYOffset || (document.documentElement || document.body).scrollTop; }
  
  function intoCoordSystem(cm, lineObj, rect, context) {
    if (lineObj.widgets) for (var i = 0; i < lineObj.widgets.length; ++i) if (lineObj.widgets[i].above) {
      var size = widgetHeight(lineObj.widgets[i]);
      rect.top += size; rect.bottom += size;
    }
    if (context == "line") return rect;
    if (!context) context = "local";
    var yOff = heightAtLine(cm, lineObj);
    if (context == "local") yOff += paddingTop(cm.display);
    else yOff -= cm.display.viewOffset;
    if (context == "page" || context == "window") {
      var lOff = getRect(cm.display.lineSpace);
      yOff += lOff.top + (context == "window" ? 0 : pageScrollY());
      var xOff = lOff.left + (context == "window" ? 0 : pageScrollX());
      rect.left += xOff; rect.right += xOff;
    }
    rect.top += yOff; rect.bottom += yOff;
    return rect;
  }
  
  
  function fromCoordSystem(cm, coords, context) {