Unidirectional Data Flow in React: Explained

When working with React, you may come across the term “Unidirectional Data Flow.” But what exactly does it mean?

Unidirectional Data Flow is not a concept exclusive to React, but as a JavaScript developer, this may be your first encounter with it.

In general, Unidirectional Data Flow refers to the idea that data has only one way to be transferred within an application.

In the context of React, Unidirectional Data Flow takes on the following meaning:

• The state is passed down to the view and child components.
• Actions are triggered by the view.
• Actions can update the state.
• The state change is then propagated to the view and child components.

The flow can be visualized in the following diagram:

In React, the view is a reflection of the application state. The state can only change when actions occur. When an action happens, it triggers a state update.

Thanks to one-way bindings, data cannot flow in the opposite direction (as is possible with two-way bindings), and this offers several advantages:

• It reduces the chances of errors, as you have more control over your data.
• It simplifies debugging, as you know exactly what data is coming from where.
• It improves performance, as the library is aware of the boundaries of each part of the system.

Each state is always owned by a single Component. Any data affected by this state can only impact Components below it, i.e., its children.

Changing the state of a Component will never affect its parent, siblings, or any other Component in the application - only its direct children.

This is why it’s common practice to move the state up the Component tree, allowing it to be shared among the components that need access to it.

Tags: react, unidirectional data flow, state management