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.

d.scrollbarH.firstChild.style.width =
        (d.scroller.scrollWidth - d.scroller.clientWidth + d.scrollbarH.clientWidth) + "px";
    } else {
      d.scrollbarH.style.display = "";
      d.scrollbarH.firstChild.style.width = "0";
    }
    if (needsH && needsV) {
      d.scrollbarFiller.style.display = "block";
      d.scrollbarFiller.style.height = d.scrollbarFiller.style.width = scrollbarWidth(d.measure) + "px";
    } else d.scrollbarFiller.style.display = "";
    if (needsH && cm.options.coverGutterNextToScrollbar && cm.options.fixedGutter) {
      d.gutterFiller.style.display = "block";
      d.gutterFiller.style.height = scrollbarWidth(d.measure) + "px";
      d.gutterFiller.style.width = d.gutters.offsetWidth + "px";
    } else d.gutterFiller.style.display = "";
    if (mac_geLion && scrollbarWidth(d.measure) === 0) {
      d.scrollbarV.style.minWidth = d.scrollbarH.style.minHeight = mac_geMountainLion ? "18px" : "12px";
      d.scrollbarV.style.pointerEvents = d.scrollbarH.style.pointerEvents = "none";
    }
  }
  function visibleLines(display, doc, viewPort) {
    var top = display.scroller.scrollTop, height = display.wrapper.clientHeight;
    if (typeof viewPort == "number") top = viewPort;
    else if (viewPort) {top = viewPort.top; height = viewPort.bottom - viewPort.top;}
    top = Math.floor(top - paddingTop(display));
    var bottom = Math.ceil(top + height);
    return {from: lineAtHeight(doc, top), to: lineAtHeight(doc, bottom)};
  }
  
  function alignHorizontally(cm) {