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 scrollPos = calculateScrollPos(cm, x1, y1, x2, y2);
    if (scrollPos.scrollTop != null) setScrollTop(cm, scrollPos.scrollTop);
    if (scrollPos.scrollLeft != null) setScrollLeft(cm, scrollPos.scrollLeft);
  }
  function calculateScrollPos(cm, x1, y1, x2, y2) {
    var display = cm.display, snapMargin = textHeight(cm.display);
    if (y1 < 0) y1 = 0;
    var screen = display.scroller.clientHeight - scrollerCutOff, screentop = display.scroller.scrollTop, result = {};
    var docBottom = cm.doc.height + paddingVert(display);
    var atTop = y1 < snapMargin, atBottom = y2 > docBottom - snapMargin;
    if (y1 < screentop) {
      result.scrollTop = atTop ? 0 : y1;
    } else if (y2 > screentop + screen) {
      var newTop = Math.min(y1, (atBottom ? docBottom : y2) - screen);
      if (newTop != screentop) result.scrollTop = newTop;
    }
    var screenw = display.scroller.clientWidth - scrollerCutOff, screenleft = display.scroller.scrollLeft;
    x1 += display.gutters.offsetWidth; x2 += display.gutters.offsetWidth;
    var gutterw = display.gutters.offsetWidth;
    var atLeft = x1 < gutterw + 10;
    if (x1 < screenleft + gutterw || atLeft) {
      if (atLeft) x1 = 0;
      result.scrollLeft = Math.max(0, x1 - 10 - gutterw);
    } else if (x2 > screenw + screenleft - 3) {
      result.scrollLeft = x2 + 10 - screenw;
    }
    return result;
  }
  function updateScrollPos(cm, left, top) {