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 (this.type != "bookmark") pos = pos.from;
    var line = getLine(this.doc, pos.line);
    clearCachedMeasurement(cm, line);
    if (pos.line >= cm.display.showingFrom && pos.line < cm.display.showingTo) {
      for (var node = cm.display.lineDiv.firstChild; node; node = node.nextSibling) if (node.lineObj == line) {
        if (node.offsetHeight != line.height) updateLineHeight(line, node.offsetHeight);
        break;
      }
      runInOp(cm, function() {
        cm.curOp.selectionChanged = cm.curOp.forceUpdate = cm.curOp.updateMaxLine = true;
      });
    }
  };
  TextMarker.prototype.attachLine = function(line) {
    if (!this.lines.length && this.doc.cm) {
      var op = this.doc.cm.curOp;
      if (!op.maybeHiddenMarkers || indexOf(op.maybeHiddenMarkers, this) == -1)
        (op.maybeUnhiddenMarkers || (op.maybeUnhiddenMarkers = [])).push(this);
    }
    this.lines.push(line);
  };
  TextMarker.prototype.detachLine = function(line) {
    this.lines.splice(indexOf(this.lines, line), 1);
    if (!this.lines.length && this.doc.cm) {
      var op = this.doc.cm.curOp;
      (op.maybeHiddenMarkers || (op.maybeHiddenMarkers = [])).push(this);
    }
  };
  var nextMarkerId = 0;
  function markText(doc, from, to, options, type) {