React Components Explained

By Bernie FitzGerald •  Updated: 07/02/23 •  4 min read

React, a widely used JavaScript library for building user interfaces introduces a modular and reusable approach to web development. At the heart of React’s philosophy lies the concept of components. In this article, we will explore the fundamentals of React components, their role in code implementation, and how they differ from other web technologies.

Conceptual Understanding of Components

In React, a component can be considered a self-contained, reusable building block that encapsulates a specific piece of functionality and UI. Conceptually, components represent independent and reusable parts of a web application, similar to building blocks that can be combined to create complex user interfaces.

React components follow a hierarchical structure, where higher-level components can contain lower-level components, forming a component tree. This tree-like structure allows for easy composition and organization of the user interface.

Components in Code

React components are implemented using JavaScript classes or, more commonly, through the functional component syntax introduced in React 16.8. The functional component approach leverages the power of JavaScript functions to create reusable UI elements.

A component consists of two main parts: the component’s code logic and its associated UI rendering. The code logic handles the internal state management, event handling, and data manipulation, while the rendering part defines how the component should appear on the screen.

React components utilize a declarative approach, meaning developers describe how the UI should look based on the component’s state and props. This declarative nature allows React to efficiently update and render only the necessary parts of the user interface, leading to improved performance.

Difference from Other Web Technologies

React components differ in several ways from traditional web technologies, such as plain HTML, CSS, and JavaScript.

  1. Reusability: React components promote reusability by encapsulating the UI and the logic within a single entity. Developers can build modular, self-contained components that they can reuse across different parts of an application or even share between projects.
  2. Component-Based Architecture: React’s component-based architecture encourages the decomposition of complex UIs into smaller, manageable parts. Each component can be developed and tested independently, facilitating code maintainability and scalability.
  3. Virtual DOM: React introduces a virtual representation of the Document Object Model (DOM). The virtual DOM allows React to efficiently update and render components by calculating the minimal changes required to reflect the updated state, rather than re-rendering the entire UI.
  4. Unidirectional Data Flow: React follows a unidirectional data flow, where data flows from parent components to child components. This approach improves predictability and makes it easier to understand how changes in state affect the UI.

A Visual Example

The image above represents a typical web page layout. The green box represents the header. The purple circle is an avatar. The red box is the container for some list items. The black boxes are the list items.

List items are repetitions of a single element, each with distinct data. Any page can use the green header. Any component can make use of the avatar etc…

You can think of the list items as array items, each knowing how to draw itself based on the data supplied.

The power of React comes from the ability to reuse components across your application. This leads to smaller units for testing (making it easier to find bugs). This makes it quicker to wireframe new pages with old components.


React components are the building blocks of modern web development, enabling developers to create reusable, modular, and maintainable user interfaces. By understanding the conceptual nature of components, their implementation in code, and their distinguishing features compared to other web technologies, developers can harness the full power of React and build robust applications efficiently.

Remember, as you delve deeper into React development, exploring the rich ecosystem of component libraries and best practices will further enhance your ability to create exceptional user experiences.

Don’t forget to check out my other React articles here. Thanks for reading!

Bernie FitzGerald

Keep Reading