When does a component unmount?

Question

My current understanding is that a component mounts onto the DOM when it is needed to be seen or when the route requires that component. It will also render its child compon

Answer 1

I would say a component mount onto the DOM only if it's used via another component, including a Router component. Don't think of routers as special elements/things in React. They're like other components and they do a matching between current URL and the patterns they have to decide which component should be rendered via the render() function of Router. Whenever there is a change of URL, the router picks the new component to render and does rendering via render() function.