Earlier in this lesson, you used the view.ui.add() method in MapView and SceneView to add API widgets to the map interface. You can also use it to add your own custom widgets built with HTML text and form elements.
See the Pen Custom Map Widgets by Jim Detwiler (@jimdetwiler) on CodePen.
The example above shows a few ways to add your own HTML widgets to the map interface. Notice the use of Esri's CSS class "esri-widget" so that they match Esri's theme. For simplicity, I've only included the code for creating and placing widgets in this example. Programming actions was described earlier in the lesson.