In this section, you're going to write some React code that sets the state of components. First, you'll learn about the initial state—that is, the default state of a component. Next, you'll learn how to change the state of a component, causing it to re-render itself. Finally, you'll see how a new state is merged with an existing state.
Setting an initial component state
The initial state of a component isn't actually required, but if your component uses state, it should be set. This is because if the component expects certain state properties to be there and they aren't, then the component will either fail or render something unexpected. Thankfully, it's easy to set the initial component state.
The initial state of a component should always be an object with one or more properties. For example, you might have a component that uses a single array as its state. This is fine, but just make sure that you set the initial array...