Optional
Called immediately before mounting occurs, and before Component.render. Avoid introducing any side-effects or subscriptions in this method.
Note: the presence of getSnapshotBeforeUpdate or StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps prevents this from being invoked.
16.3, use componentDidMount or the constructor instead; will stop working in React 17
Called immediately before mounting occurs, and before Component.render. Avoid introducing any side-effects or subscriptions in this method.
Note: the presence of getSnapshotBeforeUpdate or StaticLifecycle.getDerivedStateFromProps getDerivedStateFromProps prevents this from being invoked.