In React, Props and State are the two primary ways to manage and share data within an application. While both are plain JavaScript objects that influence a component’s output, they serve distinct roles in data flow.
Core Comparison
| Feature | Props (Properties) | State |
|---|---|---|
| Ownership | Managed by the parent component. | Managed internally by the component itself. |
| Mutability | Immutable (read-only) for the receiving component. | Mutable; can be updated by the component. |
| Purpose | Passing data and event handlers down the tree. | Managing local, dynamic data that changes over time. |
| Data Flow | Unidirectional (top-to-bottom). | Stays local to the component (unless passed as props). |
| Update Method | Updated by the parent re-rendering. | Updated via useState hook or setState method. |
Understanding Props
Props function like arguments to a function. They allow a parent component to configure its children, making components reusable.
- Immutability: A child component cannot modify the props it receives. If the data needs to change, the parent must update its state and pass the new value down.
- Communication: Props can also pass functions (callbacks). This allows child components to “talk back” to parents by triggering actions that update the parent’s state.
Understanding State
State is the component’s “memory”. It handles interactive data such as form inputs, toggle switches, or data fetched from an API.
- Reactivity: When a component’s state changes, React automatically re-renders that component and its children to reflect the update in the UI.
- Local Management: Every instance of a component maintains its own independent state. For example, two buttons using the same
Countercomponent will each track their own click count.
