# react-window
> React components for efficiently rendering large lists and tabular data
React window works by only rendering *part* of a large data set (just enough to fill the viewport). This helps address some common performance bottlenecks:
1. It reduces the amount of work (and time) required to render the initial view and to process updates.
2. It reduces the memory footprint by avoiding over-allocation of DOM nodes.
[](https://yarnpkg.com/en/package/react-window) [](https://travis-ci.org/bvaughn/react-window) [](LICENSE.md) [](#backers) [](#sponsors)
### Sponsors
The following wonderful companies have sponsored react-window:
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[Learn more about becoming a sponsor!](https://opencollective.com/react-window#sponsor)
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## Install
```bash
# Yarn
yarn add react-window
# NPM
npm install --save react-window
```
## Usage
Learn more at [react-window.now.sh](https://react-window.now.sh/):
## Related libraries
* [`react-virtualized-auto-sizer`](https://npmjs.com/package/react-virtualized-auto-sizer): HOC that grows to fit all of the available space and passes the width and height values to its child.
* [`react-window-infinite-loader`](https://npmjs.com/package/react-window-infinite-loader): Helps break large data sets down into chunks that can be just-in-time loaded as they are scrolled into view. It can also be used to create infinite loading lists (e.g. Facebook or Twitter).
* [`react-vtree`](https://www.npmjs.com/package/react-vtree): Lightweight and flexible solution to render large tree structures (e.g., file system).
## Frequently asked questions
### How is `react-window` different from `react-virtualized`?
I wrote `react-virtualized` several years ago. At the time, I was new to both React and the concept of windowing. Because of this, I made a few API decisions that I later came to regret. One of these was adding too many non-essential features and components. Once you add something to an open source project, removing it is pretty painful for users.
`react-window` is a complete rewrite of `react-virtualized`. I didn't try to solve as many problems or support as many use cases. Instead I focused on making the package **smaller**<sup>1</sup> and **faster**. I also put a lot of thought into making the API (and documentation) as beginner-friendly as possible (with the caveat that windowing is still kind of an advanced use case).
If `react-window` provides the functionality your project needs, I would strongly recommend using it instead of `react-virtualized`. However if you need features that only `react-virtualized` provides, you have two options:
1. Use `react-virtualized`. (It's still widely used by a lot of successful projects!)
2. Create a component that decorates one of the `react-window` primitives and adds the functionality you need. You may even want to release this component to NPM (as its own, standalone package)! 🙂
<sup>1 - Adding a `react-virtualized` list to a CRA project increases the (gzipped) build size by ~33.5 KB. Adding a `react-window` list to a CRA project increases the (gzipped) build size by <2 KB.</sup>
### Can a list or a grid fill 100% the width or height of a page?
Yes. I recommend using the [`react-virtualized-auto-sizer` package](https://npmjs.com/package/react-virtualized-auto-sizer):
<img width="336" alt="screen shot 2019-03-07 at 7 29 08 pm" src="https://user-images.githubusercontent.com/29597/54005716-50f41880-410f-11e9-864f-a65bbdf49e07.png">
Here's a [Code Sandbox demo](https://codesandbox.io/s/3vnx878jk5).
### Why is my list blank when I scroll?
If your list looks something like this...
<img src="https://user-images.githubusercontent.com/29597/54005352-eb535c80-410d-11e9-80b2-d3d02db1f599.gif" width="302" height="152">
...then you probably forgot to use the `style` parameter! Libraries like react-window work by absolutely positioning the list items (via an inline style), so don't forget to attach it to the DOM element you render!
<img width="257" alt="screen shot 2019-03-07 at 7 21 48 pm" src="https://user-images.githubusercontent.com/29597/54005433-45ecb880-410e-11e9-8721-420ff1a153da.png">
### Can I lazy load data for my list?
Yes. I recommend using the [`react-window-infinite-loader` package](https://npmjs.com/package/react-window-infinite-loader):
<img width="368" alt="screen shot 2019-03-07 at 7 32 32 pm" src="https://user-images.githubusercontent.com/29597/54006733-653a1480-4113-11e9-907b-08ca5e27b3f9.png">
Here's a [Code Sandbox demo](https://codesandbox.io/s/5wqo7z2np4).
### Can I attach custom properties or event handlers?
Yes, using the `outerElementType` prop.
<img width="412" alt="Screen Shot 2019-03-12 at 8 58 09 AM" src="https://user-images.githubusercontent.com/29597/54215333-f9ee9a80-44a4-11e9-9142-34c67026d950.png">
Here's a [Code Sandbox demo](https://codesandbox.io/s/4zqx79nww0).
### Can I add padding to the top and bottom of a list?
Yes, although it requires a bit of inline styling.
<img width="418" alt="Screen Shot 2019-06-02 at 8 38 18 PM" src="https://user-images.githubusercontent.com/29597/58774454-65ad4480-8576-11e9-8889-07044fd41393.png">
Here's a [Code Sandbox demo](https://codesandbox.io/s/react-window-list-padding-dg0pq).
### Can I add gutter or padding between items?
Yes, although it requires a bit of inline styling.
<img width="416" alt="Screen Shot 2019-03-26 at 6 33 56 PM" src="https://user-images.githubusercontent.com/29597/55043972-c14ad700-4ff5-11e9-9caa-2e9f4d85f96c.png">
Here's a [Code Sandbox demo](https://codesandbox.io/s/2w8wmlm89p).
### Does this library support "sticky" items?
Yes, although it requires a small amount of user code. Here's a [Code Sandbox demo](https://codesandbox.io/s/0mk3qwpl4l).
## License
MIT © [bvaughn](https://github.com/bvaughn)
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