react-window-infinite-scroll

react-window-infinite-scroll is a infinite scroll library specifically designed for react-window.

github link: https://github.com/dlguswo333/react-window-infinite-scroll npm link: https://www.npmjs.com/package/react-window-infinite-scroll

Why react-window-infinite-scroll?

react-window-infinite-scroll is to reliably load more items even when the following conditions hold:

loadMoreItems callback might cancel fetching more items.
There are not enough initial items to fill the scrollable element, thereby no way to induce onItemsRendered callback.
Not only do you need to scroll infinitely to the end, but also to the top.

Props (Properties)

type Props = {
  /** Return whether an item at the index has been loaded. */
  isItemLoaded: (index: number) => boolean;
  /**
   * Callback to load more items.
   * Receives a parameter `'start'` or `'end'` to load items at the start or end.
   */
  loadMoreItems: (direction: Direction) => Promise<unknown> | unknown;
  /**
   * Callback to be called when items have been rendered.
   * This prop is optional.
   */
  onItemsRendered?: OnItemsRendered;
  /** Returns the number of items. Can be arbitrary large if the total size is unknown. */
  itemCount: number;
  /**
   * Threshold value to load more items on items rendered.
   * When 1st ~ *threshold*th first item at either end is visible, `loadMoreItems` will be called.
   * Setting the value `0` or smaller may disable calling `loadMoreItems` on items rendered.
   */
  threshold: number;
  /**
   * offset value (in `px`) for smooth infinite scrolling.
   * Recommends value equal to minimum height of items or higher.
  */
  scrollOffset: number;
  /** children that receives `onItemsRendered` props and returns `ReactNode`. */
  children: ({onItemsRendered}: {onItemsRendered: OnItemsRendered}) => ReactNode;
  /** `ref` to the outer continer element. Passing the HTML element directly is also permitted. */
  outerRef: React.RefObject<HTMLElement> | HTMLElement;
  /** *Actual* data that needs to be virtually scrolled. */
  data: unknown[];
}

How to Use

Here is a simple example where you can do infinite scroll with react-window-infinite-scroll.

<InfiniteScroll
  data={data}
  loadMoreItems={loadMoreItems}
  isItemLoaded={isItemsLoaded}
  itemCount={itemCount}
  threshold={1}
  outerRef={outerRef}
  scrollOffset={30}
>
  {({onItemsRendered}) => <FixedSizeList
    height={300}
    itemCount={itemCount}
    width='100%'
    onItemsRendered={onItemsRendered}
    itemSize={30}
    outerRef={outerRef}
    className='Outer'
  >
    {Row}
  </FixedSizeList>}
</InfiniteScroll>

FAQ

What is the required version of `react`?

You need to have react 17 or higher because we utilize new JSX transform.

In which cases `loadMoreitems` might cancel loading more items?

In some cases, where loadMoreItems API author does not like it to be called too frequently, he/she might add a conditional statement. The reasons for this may vary, from improving browser performance to preventing server overload.

The following is an example code where loadMoreItems might cancel fetching more items.

const loadMoreItems = () => {
  if (isFetchingAlready) {
    return;
  }
  isFetchingAlready = true;
  fetchItems();
  isFetchingAlready = false;
}

In this case, some infinite scrolling packages do not work due to the blocking. However, react-window-infinite-scroll tries its best to mitigate the problem, by subscribing to both data changes and item rendered events.
When fetching is complete, the conditional value will be reset, and then the data changes or item render events will be fired afterwards.

Why `scrollOffset` prop is not optional?

scrollOffset shall not be optional since it is crucial to load more items. With it being optional, infinite scroll could have not loaded more items when the outer element's height and the inner element's height are almost equal. thus onItemsRendered is not likely to be called, and also scrollOffset is too small to call loadMoreItems.

That is why we recommend you set the value as big as the minimum height of items being rendered.

Why subscribe to both data change events and `onItemsRendered`?

This is to load more items reliably. When many rows are loaded at once, data change events would most likely not to load more items since the scrollbar is not near the bottom or the top. Later on, when you scroll the component, onItemsRendered will fire and load more items in that case.

In another case, where you have as many rows as the infinite scrolling component is barely filled, onItemsRendered would most likely not to be called, (Especially when you have big overscanCount prop value of react-window.) even though you have tiny (too tiny!) scrollable height. Data change event will help load more items in that case.

`loadMoreItems` is getting called too many/few times.

There maybe several bugs and issues with the package. Some possible issues with the component are that it may call loadMoreItems too many times, or that it may not call loadMoreItems.

One feasible reason why it calls loadMoreItems too many times is that loadMoreItems does not await until data changes and return. This is because react-window-infinite-scroll tries to prevent excessive loadMoreItems calls for performance, by waiting for loadMoreItems to finish one at a time.
Even if loadMoreItems finishes earlier than data changes, the package might not notice it and call loadMoreItems and recall once more when data changes. If loadMoreItems has something to do with promises, wait for the responses and update the data. Please do not exit right after making API calls since it can lead to undefined behaviors.

// Please don't do this ✖️
const loadMoreItems = () => {
  fetchFromRemote().then((response) => {
    setData(data => [...data, response]);
  });
};

// Or this ✖️
const loadMoreItems = () => {
  fetchFromRemote((response) => {
    setData(data => [...data, response]);
  });
};

// Please do this ✔️
const loadMoreItems = async () => {
  const response = await fetchFromRemote();
  setData(data => [...data, response]);
};

Changelog

v0.0.7

Update dependencies

v0.0.6

Revert deleted force rerendering code (Refer to v0.0.5).
Force rerender only if the data has been changed.

v0.0.5

Remove force rerendering code as it may fall into an infinite rerendering loop.

v0.0.4

Improve loadMoreItems may not execute properly.
- Fix loadMoreItems may not work when it loads items synchronously.
- Fix loadMoreItems may not work if rerendering runs before the returned promise resolves.
- Fix items may not be loaded.
Add playwright test codes

v0.0.3

Fix an error where outerRef has null or undefined value.

v0.0.2

Allow outerRef prop to have HTMLElement type
Improve README

Development

Deploy

npm run deploy

Do not run npm publish in root directory or it might publish monorepo project. We have private:true in root package.json to prevent the situation.

Test

test.Dockerfile builds an docker image for test. The dockerfile will run the test cases while building. You don't need the output image. The recommended shell command to test with docker is the following:

docker build --output type=tar,dest=/dev/null -f ./package/test.Dockerfile --network host ./package