A library app created using React.
I used the official React guide to give me structure when building this simple app.
When you have a separate component that needs to access the state of a parent or component higher up, you should use props to move up the component chain.
First you should create a copy of the state that you are changing, modify it, then replace the current state with the updated one as you cannot do all this in a single setState call.
View it here