# react-window-infinite-loader > InfiniteLoader component inspired by react-virtualized but for use with [react-window](https://github.com/bvaughn/react-window/) ### If you like this project, 🎉 [become a sponsor](https://github.com/sponsors/bvaughn/) or ☕ [buy me a coffee](http://givebrian.coffee/) ## Install ```bash # Yarn yarn add react-window-infinite-loader # NPM npm install --save react-window-infinite-loader ``` ## Documentation | Name | Type | Description | | --- | --- | --- | | `children` | `({ onItemsRendered: Function, ref: React$Ref }) => React$Node` | Render prop. See below for example usage. | | `isItemLoaded` | `(index: number) => boolean` | Function responsible for tracking the loaded state of each item. | | `itemCount` | `number` | Number of rows in list; can be arbitrary high number if actual number is unknown. | | `loadMoreItems` | `(startIndex: number, stopIndex: number) => Promise` | Callback to be invoked when more rows must be loaded. It should return a Promise that is resolved once all data has finished loading. | | `minimumBatchSize` | `?number` | Minimum number of rows to be loaded at a time; defaults to 10. This property can be used to batch requests to reduce HTTP requests. | | `threshold` | `?number` | Threshold at which to pre-fetch data; defaults to 15. A threshold of 15 means that data will start loading when a user scrolls within 15 rows. | ## Example usage The snippet below shows a basic example of how the `InfiniteLoader` can be used to wrap either a `FixedSizeList` or `VariableSizeList` from `react-window`. ```js // This value is arbitrary. // If you know the size of your remote data, you can provide a real value. // You can also increase this value gradually (as shown in the example below). const itemCount = 1000; {({ onItemsRendered, ref }) => ( )} ``` [Try it on Code Sandbox](https://codesandbox.io/s/5wqo7z2np4) ## Creating an infinite loading list The `InfiniteLoader` component was created to help break large data sets down into chunks that could be just-in-time loaded as they were scrolled into view. It can also be used to create infinite loading lists (e.g. Facebook or Twitter). Here's a basic example of how you might implement that: ```jsx function ExampleWrapper({ // Are there more items to load? // (This information comes from the most recent API request.) hasNextPage, // Are we currently loading a page of items? // (This may be an in-flight flag in your Redux store for example.) isNextPageLoading, // Array of items loaded so far. items, // Callback function responsible for loading the next page of items. loadNextPage }) { // If there are more items to be loaded then add an extra row to hold a loading indicator. const itemCount = hasNextPage ? items.length + 1 : items.length; // Only load 1 page of items at a time. // Pass an empty callback to InfiniteLoader in case it asks us to load more than once. const loadMoreItems = isNextPageLoading ? () => {} : loadNextPage; // Every row is loaded except for our loading indicator row. const isItemLoaded = index => !hasNextPage || index < items.length; // Render an item or a loading indicator. const Item = ({ index, style }) => { let content; if (!isItemLoaded(index)) { content = "Loading..."; } else { content = items[index].name; } return

{content}

; }; return ( {({ onItemsRendered, ref }) => ( {Item} )} ); } ``` [Try it on Code Sandbox](https://codesandbox.io/s/x70ly749rq) ## Advanced usage Some use cases require cached items to be reset. For example, after a list has been sorted, previously cached items may be invalid. You can let `InfiniteLoader` know that it needs to reload cached items by calling the `resetloadMoreItemsCache` method. ```jsx function ExampleWrapper({ // ... sortOrder, }) { // We create a reference for the InfiniteLoader const infiniteLoaderRef = useRef(null); const hasMountedRef = useRef(false); // Each time the sort prop changed we called the method resetloadMoreItemsCache to clear the cache useEffect(() => { // We only need to reset cached items when "sortOrder" changes. // This effect will run on mount too; there's no need to reset in that case. if (hasMountedRef.current) { if (infiniteLoaderRef.current) { infiniteLoaderRef.current.resetloadMoreItemsCache(); } } hasMountedRef.current = true; }, [sortOrder]); // ... // We passed down the ref to the InfiniteLoader component return ( {({ onItemsRendered, ref }) => ( // ... )} ); } ``` [Try it on Code Sandbox](https://codesandbox.io/embed/lucid-tree-7wnrq) ## License MIT © [bvaughn](https://github.com/bvaughn)

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