What does `class Popup extends DivOverlay<LeafletElement, Props>` syntax mean in javascript?

Question

I am working a lot with react-leaflet, and I see that part of the way it is constructed is using syntax like this:

class Popup extends DivOverlay<LeafletElement, Props>

and

export default withLeaflet<Props, Popup>(Popup)

I found some answers that were more geared towards Java. What does this mean in javascript, and specifically in the context of React and React higher order components?

Answer 1

This is statically typing components using TypeScript, which you can find a guide to here .

It essentially shapes what the data looks like for props and state for the component in question. In your case, either Popup or withLeaflet as both are components.