This is a React example project, to demonstrate my point on a blog post I publish. Basically, I'm trying to show here three diffrent approach to work with a Parent-Child components relation, where the parent component needs to know at some point of time, the values of the internal state of the Child component. In this example you will see:

Solution	Difficulty	Organization	Performance
Solution 1: Elevating state to the parent	Low	Low	Medium
Solution 2: Global State with Context-API	Medium	Hight	Medium
Solution 3: Managing state on child	Low - Medium	Hight	Hight

This is a create-react-app so you can fork, and test your self. Use yarn start or npm start to test it, or got to this app where is deployed:

https://adrianfdez469.github.io/keep-react-child-state-on-child/