Mastering React Virtualization with react-window

As web applications continue to grow in complexity and scale, the need for performance optimization becomes increasingly crucial. One of the hottest topics in the realm of frontend development is virtualization—a technique that allows applications to efficiently render only the visible portion of a large dataset. In this article, we’ll explore how to leverage react-window, a popular virtualization library, to enhance your React application’s performance.

What is React Virtualization?

React virtualization involves rendering only a small subset of a large list or grid of items. When dealing with thousands of data entries, virtualizing the UI ensures that the browser’s rendering performance remains optimal, avoiding the dreaded slowdown. This method conserves both memory and processing power, leading to a smoother user experience.

Introducing react-window

react-window is a lightweight library created by the same developer behind react-virtualized. It provides a simple and efficient way to implement virtualization in React applications. By using react-window, developers can build performant lists and grids with minimal overhead.

Key Features of react-window

• Lightweight: The core library is minimal, focusing on essential virtualization features.
• Support for fixed or dynamic item sizes.
• Easy to use: The API is straightforward and beginner-friendly.
• High performance: Optimized rendering for large lists or grids.

Getting Started with react-window

To start using react-window, you’ll first need to install the package. You can do that using npm or yarn:

npm install react-window

yarn add react-window

Next, let’s create a basic implementation of a virtualized list.

Creating a Virtualized List

We’ll create a simple list component that renders a large number of items using react-window.

import React from 'react';
import { FixedSizeList as List } from 'react-window';

const Row = ({ index, style }) => (
    

        Row {index}
    
);

const MyList = () => {
    return (
        
            {Row}
        
    );
};

export default MyList;

In this example, we create a Row component that will represent each item in our list. The MyList component then uses the List component from react-window to render 1000 rows, each with a height of 35 pixels.

Understanding List Props

Let’s take a closer look at the props we used with the List component:

• height: The height of the virtual list.
• itemCount: The total number of items in the list.
• itemSize: The height of each item in pixels. This can be fixed-size or dynamic depending on the use case.
• width: The width of the virtual list.

Advanced Virtualization Techniques

While the basic usage of react-window is straightforward, there are advanced scenarios where you may want to implement additional features. Here’s a look at some techniques to customize your virtual list.

Dynamic Item Sizes

If your items have varying heights, you can utilize VariableSizeList instead of FixedSizeList. This way, you can define heights on a per-item basis.

import React from 'react';
import { VariableSizeList as List } from 'react-window';

const items = new Array(1000).fill(true).map((_, index) => {
    return index % 2 === 0 ? 50 : 100; // Alternate heights
});

const getItemSize = (index) => items[index];

const Row = ({ index, style }) => (
    

        Row {index} - Height: {getItemSize(index)}px
    
);

const MyVariableSizeList = () => {
    return (
        
            {Row}
        
    );
};

export default MyVariableSizeList;

In this example, we defined an array of varying item sizes and used a function to determine the height as per the index of the item.

Scrolling to Items

react-window also allows programmatic scrolling. While rendering large lists, it might be useful to jump to a specific item based on user interaction. You can achieve this using the scrollToItem prop.

const MyListWithScrolling = () => {
    const listRef = React.useRef();

    const scrollToIndex = (index) => {
        if (listRef.current) {
            listRef.current.scrollToItem(index);
        }
    };

    return (
        
             scrollToIndex(100)}>Scroll to Row 100
            
                {Row}
            
        

import React from 'react';
import { useTable } from 'react-table';
import { FixedSizeList as List } from 'react-window';

const TableRow = ({ index, style, data }) => {
    const row = data[index];
    return (
        

            {row.name}
        
    );
};

const VirtualTable = ({ columns, data }) => {
    const { getTableProps, getTableBodyProps, rows, prepareRow } = useTable({
        columns,
        data,
    });

    const renderRow = ({ index, style }) => {
        prepareRow(rows[index]);
        return ;
    };
   
    return (
        

            
                {renderRow}
            
        
    );
};