Building Blocks of Success: Mastering Reusable Components in ReactJS with Props, State, and Testing
Tags: react, testing, javascript, tutorial
Published: 2023-02-02 17:06:58

Welcome to the world of **reusable components**! In this blog post, we’ll be discussing the benefits of using reusable components in **ReactJS** and how they can be created and managed. So, put on your favorite stickers, grab a snack, and let’s dive in!

First things first, **what are reusable components?** Simply put, reusable components are pieces of code that can be used multiple times throughout an application. They’re like the ultimate Lego pieces for your code. They save you time, make your code more modular, and make it easier to maintain.

**Reusable components** are like the ultimate Lego pieces for your code. They save you time, make your code more modular, and make it easier to maintain.

Using reusable components has many benefits. For one, it makes your code more modular, which means that it’s easier to understand and maintain. Each component only has to worry about its own functionality, which makes it easier to make changes or add new features. It also helps to keep your code DRY (Don’t Repeat Yourself), which reduces the chances of bugs and makes it easier to update your application.

Here’s an example of a reusable button component:

```
import React from 'react';

const Button = ({ label }) => {
  return (
    <button>{label}</button>
  );
}

export default Button;
```
In this example, we have a simple button component that takes in a label prop and displays that label on the button. Now, we can use this button component anywhere in our application, making it easy to reuse and maintain.

**Reusable components** can also be managed using props and state. **Props** are used to pass data from a parent component to a child component, and **state** is used to manage the data and behavior of a component. Here’s an example of a reusable text input component that uses props and state:

```
import React, { useState } from 'react';

const TextInput = ({ label }) => {
  const [value, setValue] = useState('');

  return (
    <div>
      <label>{label}</label>
      <input
        type="text"
        value={value}
        onChange={event => setValue(event.target.value)}
      />
    </div>
  );
}

export default TextInput;
```

In this example, we have a text input component that takes in a label prop and displays that label as the input’s label. We also use the **useState** hook to manage the value state of the input, which allows the component to update its own value as the user types.

Another great thing about **reusable components** is that they can be composed to create more complex components. For example, you can use a reusable button component and a reusable text input component to create a reusable form component. This allows you to break down your **application into smaller, more manageable pieces, making it easier to understand and maintain**.

Here’s an example of a reusable form component that uses the button and text input components from the previous examples:

```
import React, { useState } from 'react';
import Button from './Button';
import TextInput from './TextInput';

const Form = () => {
  const [formData, setFormData] = useState({});

  const handleSubmit = () => {
    console.log(formData);
  }

  return (
    <form onSubmit={handleSubmit}>
      <TextInput
        label="Name"
        value={formData.name}
        onChange={value => setFormData({ ...formData, name: value })}
      />
      <TextInput
        label="Email"
        value={formData.email}
        onChange={value => setFormData({ ...formData, email: value })}
      />
      <Button label="Submit" onClick={handleSubmit} />
    </form>
  );
}

export default Form;
```

In this example, we have a form component that uses the reusable button and text input components. We also use the useState hook to manage the formData state, which allows the component to update its own form data as the user interacts with the form. We also added a submit button and handleSubmit function that logs the form data when the form is submitted.

Another way to manage **reusable components** is to use component libraries. There are many popular component libraries such as _**Material-UI, Ant Design, and Semantic UI React**_ that provide a wide range of pre-built, reusable components. These libraries can save you a lot of time, as you don’t have to build all the components from scratch. They also follow design guidelines, which makes it easy to make your application look polished and professional.

Another advantage of using reusable components is that it helps with testing. By breaking down your application into smaller, reusable components, you can more easily test each component individually. This makes it easier to identify and fix bugs, and also helps to ensure that new changes don’t break existing functionality. React also has a great testing library called Jest that makes it easy to write and run tests for your components.

Here’s an example of a test for the reusable button component:

```
import React from 'react';
import { render, fireEvent } from '@testing-library/react';
import Button from './Button';

test('Button component should display the label text', () => {
  const label = 'Click me';
  const { getByText } = render(<Button label={label} />);
  const button = getByText(label);

  expect(button).toBeInTheDocument();
});

test('Button component should call onClick function when clicked', () => {
  const onClick = jest.fn();
  const { getByText } = render(<Button label="Click me" onClick={onClick} />);
  const button = getByText('Click me');

  fireEvent.click(button);
  expect(onClick).toHaveBeenCalled();
});
```

In this example, we use @testing-library/react to render our button component and test that it displays the correct label text and calls the onClick function when clicked. By writing tests for each reusable component, you can ensure that each component is functioning correctly and that changes to one component do not break the functionality of the other components.

In addition to the benefits of reusable components for development, it also has a positive impact on design. By creating reusable components, you can ensure that your application has a consistent look and feel. This makes it easier for users to understand and navigate your application, and also helps to create a more professional and polished look.

**In conclusion, reusable components are a powerful tool in ReactJS that can help you build more maintainable, modular, efficient and consistent code. By breaking down your application into smaller, reusable components, you can easily test each component individually and ensure that your application has a consistent look and feel. Reusable components can also be managed with the help of props and state, and component libraries can save development time and provide a polished and professional look. Additionally, testing libraries like Jest can aid in catching bugs and ensuring the functionality of your reusable components. By mastering reusable components, you can take your coding skills to the next level and build successful applications.**