Pagination is a crucial feature in modern web applications, enabling users to navigate through large datasets or content more efficiently. In this tutorial, we'll explore how to implement pagination in a React.js application.

To follow along, you should have a basic understanding of React.js and have Node.js installed on your machine.

First, Let's setup our React App:

npx create-react-app react-pagination-tutorial
cd react-pagination-tutorial

Step 1: Fetching data

For the sake of simplicity, we'll use the JSONPlaceholder API to simulate fetching data. Open the src/App.js file and replace its contents with the following code:

import "./styles.css";
import {useEffect, useState} from 'react';

export default function App() {
  const [data, setData] = useState();
  const [currentPage, setCurrentPage] = useState(1);
  const [dataPerPage] = useState(5);

  useEffect(() =>{
    const fetchData = async () =>{
      const data = await fetch('https://jsonplaceholder.typicode.com/posts')
      const json = await data.json();
      setData(json);
    }
    fetchData();
  },[])

  const changePageNo = (number) => setCurrentPage(number);

  const lastIndex = currentPage * dataPerPage;
  const firstIndex = lastIndex -  dataPerPage;
  const currentData = data?.slice(firstIndex,lastIndex);
  return (
    <div className="App">
      {currentData && currentData.map((data) =>{
        return <ul key={data.id}>
          <li>{data.title}</li>
        </ul>
      })}
    </div>
  );
}

Code Explanation:

• We set currentPage state to keep track of the current page.
• dataPerPage is the number of posts displayed per page (in this case, 5).
• We calculate lastIndex and firstIndex to slice the data array based on the current page.
• currentData contains the posts that will be displayed on the current page.
• The changePageNo function is used to update the currentPage state when the user clicks on a different page number.

Step 2: Creating the Pagination Component

Now let's create the Pagination component and pass all the data as props(Remember to import the Pagination Component):

  return (
    <div className="App">
      {currentData && currentData.map((data) =>{
        return <ul key={data.id}>
          <li>{data.title}</li>
        </ul>
      })}
      {/* Pagination Component */}
      <Pagination
      changePageNo={changePageNo} 
      data={data?.length}
      dataPerPage={dataPerPage}
      currentPage={currentPage}
      />
    </div>
  );

This is our Pagination.js file:

export default function Pagination({
  changePageNo,
  data,
  dataPerPage,
  currentPage
}) {
  let numbers = [];
  for (let i = 1; i <= Math.ceil(data/dataPerPage) ;i++){
    numbers.push(i);
  }
  return <div>
    {numbers && numbers.map((no) =>{
      return <button key={no}
      onClick={() =>{
        changePageNo(no);
      }}
      >{no}</button>
    })}
  </div>;
}

Note that we are using a for loop runs from 1 to Math.ceil(data/dataPerPage)(inclusive). This loop calculates the total number of pages required to display all the data items based on the dataPerPage prop.

Final step: Adding styles

Now let's write some simple CSS code to set an active and a normal state for our buttons:

.active{
  background-color: black;
  color: white;
}

.normal{
  background-color: white;
  color:black;
}

Now modify the Pagination.js file to something like this:

  return <div>
    {numbers && numbers.map((no) =>{
      return <button key={no}
      // Adding active and normal state
      className={no === currentPage?"active":"normal"}
      onClick={() =>{
        changePageNo(no);
      }}
      >{no}</button>
    })}
  </div>;

The className is set based on whether the current no matches the currentPageprop. If they match, the classNamewill be set to active, indicating that the button represents the currently active page. Otherwise, it will be set to normal for non-active pages.

Conclusion

In this tutorial, we walked through creating a simple pagination component in React.js. By following the steps, you've learned how to fetch data, divide it into pages, and display the content with pagination. Feel free to customize the styling and explore other pagination libraries to enhance the user experience. If you need any help or have some suggestions, feel free to express them in the comments.

Happy coding!