In the world of programming and website development, component-based JavaScript frameworks are one of the unique tools. Frameworks React.js, one of the most popular JavaScript frameworks, provides a component-based framework that helps developers design simpler, more powerful, and more extensible websites and web applications.

In this article, the components of the React.js framework and its capabilities have been reviewed.

What is a React Component?

Parts or components in React are like puzzle pieces that together make a website or web application. In other words, each component is a specific part of a web page that performs different tasks. For example, a component to display a button, a component to display a form or even one to display a list of items.

Using components helps programmers to separate different parts of the website page and work on each part separately. Therefore, different parts of the website pages are developed independently and then put together to create a more complete part of the website.

For example, suppose you have a web page that contains a header, a form for entering information, and a list of products. You can consider each of these parts as an independent component. These components allow you to implement each part individually and then put them together and combine them to create a complete page.

Why is a component important in React?

There are important reasons for using components in React, which are mentioned in this section:

1. Degradability and reusability

When user interface elements are divided into smaller sections (eg buttons, text boxes, etc.), each section can be developed separately.

Also, the components defined in a component are reusable, that is, they can be used again.

2. Faster development

Components allow the developer to have different team members work together on different parts of the application without their work interfering with each other. This makes the development process go faster.

3. maintainability

Using components, if you change the style or function of a component, these changes are automatically applied to all parts of the program where that component is used.

Types of components in ReactJS

In React, there are two types of components:

1. Functional components:

Functional components are like JavaScript functions. Defining functional components is just like defining a function. Functional components take inputs called props (input data) and generate elements through JSX. Using this type of component, you can define different parts of the site’s UI and create them as JavaScript functions.

JSX (JavaScript Syntax Extension) is an important part of React. JSX allows the programmer to write HTML codes in JavaScript code.

2. Class Components:

Class components in React are a bit more complicated than functional components. In functional components, the focus is only on the part that is defined and there is no connection with other components. However, the components of the class work with each other and transfer information between each other.

Class components allow the developer to combine different parts of the page to better communicate with each other. However, it should be noted that if the class is used more than necessary in the code, the code may become too complicated.

Two basic concepts in React JS components

You may be wondering when it is better to use which type of component. In the list below, we have compared these two types of components so that you can make a better choice. But before that, you need to familiarize yourself with two other terms:


State in React refers to information that is stored in a component and can change over time. For example, if the button component has a state like “number of clicks”, when the user clicks on the button, the number of clicks will be updated and displayed in the state. Using state allows components to hold data so that this information is available at any time.


Hooks in React are tools that allow functional components to have properties such as state or component lifecycle. In other words, hooks give functional components extra facilities to act like class components.

What are props in the React component?

Props are like commands given to components. Props allow the developer to pass data from a parent component to a child component. Props are used to customize the code and behavior of a component based on input values.

Render the component

To display or render a component in React, the user-defined component is sent as the first parameter to the ReactDOM.render() function, or directly the component is sent as the first argument to the ReactDOM.render() method.

Note: To distinguish components from HTML tags, the name of a component must always start with a capital letter.

Components in React are powerful tools that allow developers to create attractive and dynamic user interfaces. These components are separate and usable pieces that are used to build and combine pages and different sections in website and web application design.

With management principles such as the concept of State and Hooks, React helps to create applications with better performance and simpler code.

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