Any object can be extended with any behaviour at any time, and that behaviour can be called at any time. You can write objects which aren’t classes, but groups of behaviours, and extend any other object with them when you need. Even JSON data coming in from a server can instantly be embedded with such behaviour.
Do note that, due to the newness and, ironically, the flexibility of the language, these different patterns are still being developed. It’s hard for all of us to let go of old ideas and fully embrace the new ones, and deadlines often mean not doing that new feature in the way you’ve been learning (or brainstorming). Ultimately, you and the developers who follow after you (and ultimately the company) will pay the price for such shortcuts.