---
title: Sheets at Native Speed with Lynx
sidebar_label: Lynx
description: Build data-intensive mobile apps with Lynx. Seamlessly integrate spreadsheets into your app using SheetJS. Securely process and generate Excel files in the field.
pagination_prev: demos/static/index
pagination_next: demos/desktop/index
sidebar_position: 7
sidebar_custom_props:
  summary: React + Native Rendering
---

import current from '/version.js';
import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';
import CodeBlock from '@theme/CodeBlock';

export const r = {style: {color:"red"}};
export const g = {style: {color:"green"}};
export const y = {style: {color:"gold"}};
export const gr = {style: {color:"gray"}};

[Lynx](https://lynxjs.org/) is a modern cross-platform framework. It builds iOS,
Android and Web apps that use JavaScript for describing layouts and events.

[SheetJS](https://sheetjs.com) is a JavaScript library for reading and writing
data from spreadsheets.

:::caution Lynx support is considered experimental.

Lynx is relatively new and does not currently have a deep community.

Any issues should be reported to the Lynx project for further diagnosis.

:::

This demo uses React (using [ReactLynx](https://lynxjs.org/react)) and SheetJS
to process and generate spreadsheets. We'll explore how to load SheetJS in Lynx
apps in the following scenarios:

- ["Fetching Remote Data"](#fetching-remote-data) uses the built-in `fetch` to download
and parse remote workbook files.

The "Fetching Remote Data" example creates an app that looks like the screenshots below:

<table><thead><tr>
    <th><a href="#demo">iOS</a></th>
    <th><a href="#demo">Android</a></th>
</tr></thead><tbody><tr><td>

![iOS screenshot](pathname:///lynx/react_lynx_fetch_demo_ios_1.jpeg)

</td><td>

![Android screenshot](pathname:///lynx/react_lynx_fetch_demo_android_1.png)

</td></tr></tbody></table>

:::caution pass

**Before testing this demo, follow the official React Lynx Guide!**[^1]

Follow the instructions for iOS (requires macOS) and for Android. They will
cover installation and system configuration. You should be able to build and run
a sample app in the Android and the iOS (if applicable) simulators.

:::

:::danger pass

**Lynx development requires an Apple Silicon-powered Macintosh!**

[X64 is currently unsupported.](https://github.com/lynx-family/lynx/issues/219)

:::

## Integration Details

The [SheetJS NodeJS Module](/docs/getting-started/installation/nodejs) can be
imported from any component or script in the app.

### Internal State

For simplicity, this demo uses an "Array of Arrays"[^2] as the internal state.


<table>
  <thead><tr><th>Spreadsheet</th><th>Array of Arrays</th></tr></thead>
  <tbody><tr><td>

![`pres.xlsx` data](pathname:///pres.png)

</td><td>

```js
[
  ["Name", "Index"],
  ["Bill Clinton", 42],
  ["GeorgeW Bush", 43],
  ["Barack Obama", 44],
  ["Donald Trump", 45],
  ["Joseph Biden", 46]
]
```

</td></tr></tbody></table>

Each array represents a row in the table.

This demo also keeps track of the column widths as a single array of numbers.
The widths are used by the display component.

```ts title="State variables"
const [data, setData] = useState<any[]>([
  "SheetJS".split(""),
  [5, 4, 3, 3, 7, 9, 5],
  [8, 6, 7, 5, 3, 0, 9]
]);
const [widths, setWidths] = useState<number[]>(Array.from({ length: 7 }, () => 20));
```

#### Updating State

Starting from a SheetJS worksheet object, `sheet_to_json`[^3] with the `header`
option can generate an array of arrays:

```js title="Updating state from a workbook"
/* assuming `wb` is a SheetJS workbook */
function update_state(wb) {
  /* convert first worksheet to AOA */
  const wsname = wb.SheetNames[0];
  const ws = wb.Sheets[wsname];
  const data = utils.sheet_to_json(ws, {header:1});

  /* update state */
  setData(data);

  /* update column widths */
  setWidths(make_width(data));
}
```

_Calculating Column Widths_

Column widths can be calculated by walking each column and calculating the max
data width. Using the array of arrays:

```js title="Calculating column widths"
/* this function takes an array of arrays and generates widths */
function make_width(aoa) {
  /* walk each row */
  aoa.forEach((r) => {
    /* walk each column */
    r.forEach((c, C) => {
      /* update column width based on the length of the cell contents */
      res[C] = Math.max(res[C]||60, String(c).length * 10);
    });
  });
  /* use a default value for columns with no data */
  for(let C = 0; C < res.length; ++C) if(!res[C]) res[C] = 60;
  return res;
}
```

### Displaying Data

Lynx does not ship with a component for displaying tabular data.

The demo uses Lynx `<view/>` and `<text/>` elements to display tabular data:

```tsx title="Example JSX for displaying data"
{/* Table container */}
<view className='Table'>
  {/* Map through each row in the data array */}
  {data.map((row, rowIndex) => (
    <view key={`row-${rowIndex}`} className="Row">
      {/* Map through each cell in the current row */}
      {Array.isArray(row) && row.map((cell, cellIndex) => (
        {/* Cell with dynamic width based on content */}
        <view 
          key={`cell-${rowIndex}-${cellIndex}`}  className="Cell"
          style={{ width: `${widths[cellIndex]}px` }}>
          {/* Display cell content as text */}
          <text>{String(cell)}</text>
        </view>
      ))}
    </view>
  ))}
</view>
```

## Fetching Remote Data

This snippet downloads and parses https://docs.sheetjs.com/pres.xlsx:

```js
/* fetch data into an ArrayBuffer */
const ab = await (await fetch("https://docs.sheetjs.com/pres.xlsx")).arrayBuffer();
/* parse data */
const wb = XLSX.read(ab);
```

### Fetch Demo

:::note Tested Deployments

This demo was tested in the following environments:

**Simulators**

| OS         | Device              | Lynx     | LynxExplorer | Dev Platform | Date       |
|:-----------|:--------------------|:---------|:-------------|:-------------|:-----------|
| Android 35 | Pixel 3a            | `0.8.6`  | `3.2.0-rc.1` | `darwin-arm` | 2025-03-26 |
| iOS 18.3   | iPhone 16 Pro       | `0.8.6`  | `3.2.0-rc.1` | `darwin-arm` | 2025-03-26 |

:::

:::danger Real Devices

When this demo was last tested, there was no simple standalone guide for running
Lynx apps on real devices.

:::

:::caution pass

First install Lynx by following the Guide![^1].

Make sure you can run a basic test app on your simulator before continuing!

:::

0) Install Lynx dependencies

1) Create project:

```bash
npm create rspeedy@0.8.6 -- -d SheetJSLynxFetch -t react-ts --tools biome
```

2) Install shared dependencies:

<CodeBlock language="bash">{`\
cd SheetJSLynxFetch
curl -o ./src/assets/SheetJS-logo.png https://docs.sheetjs.com/logo.png
npm i
npm i -S https://cdn.sheetjs.com/xlsx-${current}/xlsx-${current}.tgz`}
</CodeBlock>

3) Download [`App.tsx`](pathname:///lynx/App.tsx) into the `src` folder:

```bash
curl -o ./src/App.tsx https://docs.sheetjs.com/lynx/App.tsx
```

4) Download [`App.css`](pathname:///lynx/App.css) into the `src` folder:

```bash
curl -o ./src/App.css https://docs.sheetjs.com/lynx/App.css
```
<a name="step5"></a>

5) Start the development server:

```bash
npm run dev
```

Keep the window open.

#### Android

6) Start the Android emulator:

<Tabs>
  <TabItem name="Android Studio" value="Android Studio">

In Android Studio, click "More actions" > "Virtual Device Manager". Look for the
emulated device in the list and click the ▶ button to play.

  </TabItem>
  <TabItem name="Android Studio" value="Command Line">

List the available emulators with `emulator -list-avds`:

```
shjs@sheetjs SheetJSLynxFetch % emulator -list-avds
Medium_Phone_API_35
^^^^^^^^^^^^^^^^^^^--- emulator name
```

The emulator name should be passed to `emulator -avd`. In a previous test, the
name was `Medium_Phone_API_35` and the launch command was:

```bash
emulator -avd Medium_Phone_API_35
```

:::note pass

On macOS, `~/Library/Android/sdk/emulator/` is the typical location
for the `emulator` binary. If it cannot be found, add the folder to `PATH`:

```bash
export PATH="$PATH":~/Library/Android/sdk/emulator
emulator -avd Medium_Phone_API_35
```

:::

  </TabItem>
</Tabs>

7) Download the LynxExplorer[^4] APK.

The latest test used [`LynxExplorer-noasan-release.apk` for version `3.2.0-rc.1`](https://github.com/lynx-family/lynx/releases/download/3.2.0-rc.1/LynxExplorer-noasan-release.apk).

8) Drag and drop the APK into the Android emulator window.

The emulator will install LynxExplorer.

9) In the terminal window from [step 5](#step5), copy the HTTP link. It will be
printed below the QR code, as shown in the following screenshot:

![lynx live server link](pathname:///lynx/lynx_live_server_link.png)

10) In the emulator, open the "LynxExplorer" app.

11) In the **Enter Card URL** input field, paste the link. Tap **Go**.

The view will refresh. The app should look like the "Before" screenshot:

<table><thead><tr>
  <th>Before</th>
  <th>After</th>
</tr></thead><tbody><tr><td>

![before screenshot](pathname:///lynx/react_lynx_fetch_demo_android_1.png)

</td><td>

![after screenshot](pathname:///lynx/react_lynx_fetch_demo_android_2.png)

</td></tr></tbody></table>

12) Tap "Import data from a spreadsheet" and verify that the app shows new data.
The app should look like the "After" screenshot.


**iOS Testing**

:::danger pass

**iOS testing can only be performed on Apple hardware running macOS!**

Xcode and iOS simulators are not available on Windows or Linux.

:::

13) Download the LynxExplorer[^4] app tarball.

The latest test used [`LynxExplorer-arm64.app.tar.gz` for version `3.2.0-rc.1`](https://github.com/lynx-family/lynx/releases/download/3.2.0-rc.1/LynxExplorer-arm64.app.tar.gz).

14) Open `LynxExplorer-arm64.app.tar.gz` using Finder.

The tarball contains an app named `LynxExplorer-arm64` .

15) Launch the iOS Simulator.

16) Click and drag `LynxExplorer-arm64` into the Simulator window.

The simulator will install the "LynxExplorer" app.

17) Copy the HTTP link from the terminal window in [step 5](#step5).

![lynx live server link](pathname:///lynx/lynx_live_server_link.png)

18) Tap the "LynxExplorer" icon in the simulator to launch the app.

19) Tap the **Enter Card URL** input field and paste the link. Tap **Go**.

The view will refresh. The app should look like the "Before" screenshot:

<table><thead><tr>
  <th>Before</th>
  <th>After</th>
</tr></thead><tbody><tr><td>

![before screenshot](pathname:///lynx/react_lynx_fetch_demo_ios_1.jpeg)

</td><td>

![after screenshot](pathname:///lynx/react_lynx_fetch_demo_ios_2.jpeg)

</td></tr></tbody></table>

20) Tap "Import data from a spreadsheet" and verify that the app shows new data. The app should look like the "After" screenshot.

[^1]: Follow ["Quick Start"](https://lynxjs.org/guide/start/quick-start.html) in
the Lynx documentation and select the appropriate "Lynx Explorer sandbox"
[^2]: See ["Array of Arrays" in the API reference](/docs/api/utilities/array#array-of-arrays)
[^3]: See ["Array Output" in "Utility Functions"](/docs/api/utilities/array#array-output)
[^4]: See ["LynxExplorer sandbox"](https://github.com/lynx-family/lynx/releases/latest/)