Applying attributes to a text layer that's being edited in Sketch

example.js

framework("CoreText");

const DOM = require("sketch/dom");

const textLayer = DOM.getSelectedDocument().pages[0].selectedLayers.layers[0];

const textView = textLayer.sketchObject.editingDelegate().textView();

//  [NSTextView selectedRanges] returns an NSArray of NSValues:
const selectedRange = textView.selectedRanges()[0].rangeValue();

const textStorage = textView.textStorage();

textStorage.applyFontTraits_range(NSBoldFontMask, selectedRange);

textView.didChangeText(); // key for getting the NSTextView to redraw/update