Learn React Components, State and Forms for MERN Apps
Think in components
A React component describes a part of the interface. Break a screen into components with clear responsibilities—for example, a page shell, filter controls, a list and an individual card. Small components are easier to reuse and test when their purpose is clear.
Props and state
Props pass information from a parent component to a child. State represents information that can change over time, such as a selected filter or form value. Keep state as close as practical to the components that need it, and avoid storing duplicate values that can be derived from existing state.
Render collections and conditions
Use stable keys when rendering lists so React can track items as the collection changes. Conditional rendering can represent loading, empty, error and success states. These states should communicate what is happening and what the user can do next.
Forms and validation
Controlled inputs keep displayed values synchronized with component state. Labels and helpful error messages improve usability. Client-side validation can prevent obvious mistakes, but it is only a convenience; the backend must validate all incoming data independently.
Connect to API data
Fetch data through a clear service or hook rather than mixing every request detail into a large component. Consider cancellation or stale responses when users change filters quickly. Handle unsuccessful status codes and network errors, and do not treat an empty array after failure as a successful empty result.
Accessibility and maintainability
Use semantic buttons and links, support keyboard interaction, label inputs, and announce important errors appropriately. Keep components focused, name state clearly and test user-visible behavior rather than implementation details alone.