Unidirectional Data Flow in React

A component can pass its state down the tree of descendants as props to child components. This process is called top-down or unidirectional data flow. State is always owned by a specific component, and that state can only affect components that are descendants of that component.

In addition to the top-down data flow, there is also the upward. It contains data that appears in child components, such as inputs from the user. This data flow is passed to the parent by calling a function passed in the props of the child component.