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 d = cm.display, doc = cm.doc;
    d.maxLine = getLine(doc, doc.first);
    d.maxLineLength = lineLength(doc, d.maxLine);
    d.maxLineChanged = true;
    doc.iter(function(line) {
      var len = lineLength(doc, line);
      if (len > d.maxLineLength) {
        d.maxLineLength = len;
        d.maxLine = line;
      }
    });
  }
  
  
  function setGuttersForLineNumbers(options) {
    var found = indexOf(options.gutters, "CodeMirror-linenumbers");
    if (found == -1 && options.lineNumbers) {
      options.gutters = options.gutters.concat(["CodeMirror-linenumbers"]);
    } else if (found > -1 && !options.lineNumbers) {
      options.gutters = options.gutters.slice(0);
      options.gutters.splice(found, 1);
    }
  }
  
  
  
  function updateScrollbars(cm) {