16.3-blogpost-signatures.js

class Example extends React.Component<
  Props,
  State,
  Snapshot
> {
  static getDerivedStateFromProps(
    nextProps: Props,
    prevState: State
  ): $Shape<State> | null {
    // ...
  }

  getSnapshotBeforeUpdate(
    prevProps: Props,
    prevState: State
  ): Snapshot {
    // ...
  }
}

Stupid question, but is this TypeScript? The file extensions says .js.

@geekf it's Flow

Replace $Shape with Partial and you have typescript, though.

@simonbuchan just wondering... will Flow and Typescript merge?

This is Flow

How to define Snapshot?