How do you optimize the rendering of large lists or tables in React?

1 Use pagination or infinite scrolling

One way to reduce the number of items that need to be rendered at once is to use pagination or infinite scrolling. Pagination divides the list or table into multiple pages, and only renders the current page. Infinite scrolling loads more items as the user scrolls down, and removes the items that are out of view. Both methods can reduce the initial loading time and memory usage, and give the user a sense of progress. However, they also have some drawbacks, such as losing the ability to sort, filter, or jump to a specific item, or requiring more network requests and state management.

2 Use virtualization or windowing

Another way to optimize the rendering of large lists or tables is to use virtualization or windowing. Virtualization or windowing means that only the items that are visible in the viewport are rendered, and the rest are replaced by placeholders. This can significantly improve the performance and memory efficiency, as well as the smoothness of scrolling. However, virtualization or windowing also requires some extra work, such as measuring the size of each item, calculating the scroll position and offset, and handling dynamic data and resizing. Fortunately, there are some libraries that can help you implement virtualization or windowing in React, such as react-window, react-virtualized, or react-infinite.

3 Use memoization or pure components

Another technique to optimize the rendering of large lists or tables is to use memoization or pure components. Memoization or pure components means that you prevent unnecessary re-rendering of the items that have not changed, by comparing their props or state. This can avoid wasting time and resources on rendering the same items over and over again, and improve the performance and responsiveness of your application. However, memoization or pure components also have some caveats, such as adding complexity and overhead to your code, or causing bugs if you mutate the props or state directly. Therefore, you should use memoization or pure components carefully, and only when you have identified a performance bottleneck.

4 Use keys or indexes

Another tip to optimize the rendering of large lists or tables is to use keys or indexes. Keys or indexes are identifiers that help React track which items have changed, moved, or been added or removed. This can help React perform the minimum amount of DOM updates, and avoid unnecessary re-rendering or re-mounting of the items. However, keys or indexes also have some rules and best practices, such as using unique and stable keys, avoiding using indexes as keys unless the list is static, and using fragments or arrays to return multiple elements.

5 Use code splitting or lazy loading

Another strategy to optimize the rendering of large lists or tables is to use code splitting or lazy loading. Code splitting or lazy loading means that you divide your code into smaller chunks or modules, and only load them when they are needed. This can reduce the initial bundle size and loading time, and improve the user experience and performance of your application. However, code splitting or lazy loading also requires some tools and configuration, such as using dynamic imports, webpack, or React.lazy and Suspense.

6 Use profiling or debugging tools

The last technique to optimize the rendering of large lists or tables is to use profiling or debugging tools. Profiling or debugging tools can help you measure and analyze the performance of your application, identify the bottlenecks and issues, and find the best solutions. Some of the tools that you can use in React are the React DevTools, the Chrome DevTools, the Lighthouse, or the React Profiler API.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?