Attempting to set font attributes during selection

SetAttribtuesWhileEditing.js

const Sketch = require('sketch')
framework("CoreText");

let myTextLayer = Sketch.getSelectedDocument().selectedLayers.layers[0]

let textLayer = myTextLayer.sketchObject
if (textLayer.isEditingText() == 0) {
  console.log("select some text")

} else {
  let textStorage = myTextLayer.sketchObject.editingDelegate().textStorage()
  // Todo: Figure out how to get the selected range / range of the text object
  let myRange = NSMakeRange(0,5)
  let myFont = textLayer.font()
  let lowerCaseFont = updateFontWithID_Key(myFont, kLowerCaseType,kLowerCaseSmallCapsSelector)

  textStorage.beginEditing()
  textStorage.addAttribute_value_range(NSFontAttributeName,lowerCaseFont,myRange)
  textStorage.fixAttributesInRange(myRange)
  textStorage.endEditing()
}

function updateFontWithID_Key(font, key, value) {
    let settingsAttribute = getSettingsAttributeForKey_value(key, value)
    const descriptor = font.fontDescriptor().fontDescriptorByAddingAttributes(settingsAttribute)
    const newFont = NSFont.fontWithDescriptor_size(descriptor,font.pointSize())
    return newFont
}

function getSettingsAttributeForKey_value(key, value) {
    let settingsAttribute = {
        [NSFontFeatureSettingsAttribute]: [{
            [NSFontFeatureTypeIdentifierKey]: key,
            [NSFontFeatureSelectorIdentifierKey]: value
        }]
    }

    return settingsAttribute
}