Sheets on the Go with React Native

React Native is a mobile app framework. It builds iOS and Android apps that use JavaScript for describing layouts and events.

SheetJS is a JavaScript library for reading and writing data from spreadsheets.

This demo uses React Native and SheetJS to process and generate spreadsheets. We'll explore how to load SheetJS in a React Native app in a few ways:

• "Fetching Remote Data" uses the built-in fetch to download and parse remote workbook files.
• "Local Files" uses native libraries to read and write files on the device.

The "Local Files" example creates an app that looks like the screenshots below:

iOS	Android

Before testing this demo, follow the official React Native CLI 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.

Integration Details

The SheetJS NodeJS Module 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.

Spreadsheet	Array of Arrays
	[ ["Name", "Index"], ["Bill Clinton", 42], ["GeorgeW Bush", 43], ["Barack Obama", 44], ["Donald Trump", 45], ["Joseph Biden", 46] ]

Each array within the structure corresponds to one row.

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

Complete State

The complete state is initialized with the following snippet:

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

Updating State

Starting from a SheetJS worksheet object, sheet_to_json³ with the header option can generate an array of arrays:

/* 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:

/* 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;
}

Exporting State

aoa_to_sheet⁴ builds a SheetJS worksheet object from the array of arrays:

/* generate a SheetJS workbook from the state */
function export_state() {
  /* convert AOA back to worksheet */
  const ws = utils.aoa_to_sheet(data);

  /* build new workbook */
  const wb = utils.book_new();
  utils.book_append_sheet(wb, ws, "SheetJS");

  return wb;
}

Displaying Data

The demos uses react-native-table-component to display the first worksheet.

The demos use components similar to the example below:

import { ScrollView } from 'react-native';
import { Table, Row, Rows, TableWrapper } from 'react-native-table-component';

(
  {/* Horizontal scroll */}
  <ScrollView horizontal={true} >
    {/* Table container */}
    <Table>
      {/* Frozen Header Row */}
      <TableWrapper>
        {/* First row */}
        <Row data={data[0]} widthArr={widths}/>
      </TableWrapper>
      {/* Scrollable Data Rows */}
      <ScrollView>
        <TableWrapper>
          {/* Remaining Rows */}
          <Rows data={data.slice(1)} widthArr={widths}/>
        </TableWrapper>
      </ScrollView>
    </Table>
  </ScrollView>
)

data.slice(1) in the Rows component returns data starting from the second row. This neatly skips the first header row.

Fetching Remote Data

React Native versions starting from 0.72.0⁵ support binary data in fetch.

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

/* 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

Tested Deployments

This demo was tested in the following environments:

Real Devices

OS	Device	RN	Date
iOS 15.1	iPhone 12 Pro Max	0.73.6	2024-03-13
Android 29	NVIDIA Shield	0.73.6	2024-03-13

Simulators

OS	Device	RN	Dev Platform	Date
Android 34	Pixel 3a	0.73.6	darwin-x64	2024-03-13
iOS 17.4	iPhone 15 Pro Max	0.73.6	darwin-x64	2024-03-13
Android 34	Pixel 3a	0.74.2	darwin-arm	2024-06-20
iOS 17.5	iPhone SE (3rd gen)	0.74.2	darwin-arm	2024-06-20
Android 34	Pixel 3a	0.73.5	win10-x64	2024-03-05
Android 34	Pixel 3a	0.73.7	linux-x64	2024-04-29

0. Install React Native dependencies

Installation Notes (click to show)

On the Steam Deck, JDK17 was installed using pacman:

sudo pacman -Syu jdk17-openjdk

The Android Studio tarball was downloaded and extracted. After extracting:

cd ./android-studio/bin
./studio.sh

In Android Studio, select "SDK Manager" and switch to the "SDK Tools" tab. Check "Show Package Details" and install "Android SDK Command-line Tools (latest)".

When this demo was last tested, the following environment variables were used:

export ANDROID_HOME=~/Android/Sdk
export PATH=$PATH:$ANDROID_HOME/emulator:$ANDROID_HOME/platform-tools
export JAVA_HOME=/usr/lib/jvm/java-17-openjdk

1. Create project:

npx -y react-native@0.74.2 init SheetJSRNFetch --version="0.74.2"

2. Install shared dependencies:

cd SheetJSRNFetch
curl -LO https://docs.sheetjs.com/logo.png
npm i -S https://cdn.sheetjs.com/xlsx-0.20.3/xlsx-0.20.3.tgz
npm i -S react-native-table-component@1.2.2 @types/react-native-table-component

3. Download App.tsx and replace:

curl -LO https://docs.sheetjs.com/reactnative/App.tsx

Android Testing

4. Install or switch to Java 17⁶

5. Start the Android emulator:

npx react-native run-android

On Linux, the command may silently stall. It is strongly recommended to launch the interactive CLI tool:

npx react-native start

Once the dev server is ready, the terminal will display a few options. Press a to run on Android.

If the initial launch fails with an error referencing the emulator, manually start the emulator from Android Studio and try again.

Gradle errors typically stem from a Java version mismatch:

> Failed to apply plugin 'com.android.internal.application'.
   > Android Gradle plugin requires Java 17 to run. You are currently using Java 11.

This error can be resolved by installing and switching to the requested version.

When this demo was last tested on Linux, the process failed to launch the emulator:

warn Please launch an emulator manually or connect a device. Otherwise app may fail to launch.

This is a known bug in React Native!

If an emulator is installed, run the following command:

npx react-native doctor

Under Android, there will be one error:

Android 

 ✖ Adb - No devices and/or emulators connected. Please create emulator with Android Studio or connect Android device.

Press f and a list of available emulators will be shown. Select the emulator (typically the last line) and press Enter.

✔ Select the device / emulator you want to use › Emulator Pixel_3a_API_34_extension_level_7_x86_64 (disconnected)

The text in green is the name of the virtual device (Pixel_3a_API_34_extension_level_7_x86_64 in this example). Run the following command to manually start the emulator:

$ANDROID_HOME/tools/emulator -avd Pixel_3a_API_34_extension_level_7_x86_64

(replace Pixel_3a_API_34_extension_level_7_x86_64 with the name of the virtual device)

To confirm React Native detects the emulator, run the following command again:

npx react-native doctor

6. When opened, the app should look like the "Before" screenshot below. After tapping "Import data from a spreadsheet", verify that the app shows new data:

Before	After

iOS Testing

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

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

7. Refresh iOS project by running pod install from the ios subfolder:

cd ios; pod install; cd -

8. Start the iOS emulator:

npx react-native run-ios

9. When opened, the app should look like the "Before" screenshot below. After tapping "Import data from a spreadsheet", verify that the app shows new data:

Before	After

Android Device Testing

10. Connect an Android device using a USB cable.

If the device asks to allow USB debugging, tap "Allow".

11. Close any Android / iOS emulators.

12. Build APK and run on device:

npx react-native run-android

iOS Device Testing

13. Connect an iOS device using a USB cable.

If the device asks to trust the computer, tap "Trust" and enter the passcode.

14. Close any Android / iOS emulators.

15. Enable developer code signing certificates⁷.

Enabling Code Signing (click to show)

These instructions were verified against Xcode 15.3.

A) Open the included iOS workspace in Xcode:

open ios/SheetJSRNFetch.xcworkspace

B) Select "SheetJSRNFetch" in the Project Navigator:

C) Select "Signing & Capabilities" in the main view.

D) Select "All" in the lower bar and ensure a Team is selected in the dropdown:

16. Install ios-deploy through Homebrew:

brew install ios-deploy

17. Run on device:

npx react-native run-ios

In some tests, the app failed to run on the device due to "Untrusted Developer":

Your device management settings do not allow apps from developer ... on this iPhone. You can allow using these apps in Settings.

These instructions were verified against iOS 15.1.

A) Open the Settings app and select "General" > "VPN & Device Management".

B) Select the Apple Development certificate under "Developer App".

In the new screen, the name "SheetJSRNFetch" will be displayed in the Apps list.

C) Tap "Trust ..." and tap "Trust" in the popup.

D) Close the Settings app on the device.

E) Close the Metro window on the computer.

F) Run npx react-native run-ios again.

In some tests, the build failed with the following error:

PhaseScriptExecution failed with a nonzero exit code

This was due to an error in the react-native package. The script node_modules/react-native/scripts/react-native-xcode.sh must be edited.

Near the top of the script, there will be a set statement:

node_modules/react-native/scripts/react-native-xcode.sh

# Print commands before executing them (useful for troubleshooting)
set -x -e
DEST=$CONFIGURATION_BUILD_DIR/$UNLOCALIZED_RESOURCES_FOLDER_PATH

The -e argument must be removed:

node_modules/react-native/scripts/react-native-xcode.sh (edit line)

# Print commands before executing them (useful for troubleshooting)
set -x
DEST=$CONFIGURATION_BUILD_DIR/$UNLOCALIZED_RESOURCES_FOLDER_PATH

In some test runs, the error mentioned a development team:

error: Signing for "SheetJSRNFetch" requires a development team. Select a development team in the Signing & Capabilities editor. (in target 'SheetJSRNFetch' from project 'SheetJSRNFetch')

Code signing must be enabled in the project!

By default, React Native generates applications that exclusively target iPhone. On a physical iPad, a pixellated iPhone app will be run.

The "targeted device families" setting must be changed to support iPad:

A) Open the Xcode workspace:

open ./ios/SheetJSRNFetch.xcworkspace

B) Select the project in the left sidebar:

C) Select the "SheetJSRNFetch" target in the sidebar.

D) Select the "Build Settings" tab in the main area.

E) In the search bar below "Build Settings", type "tar"

F) In the "Targeted Device Families" row, change the value to "iPhone, iPad".

In some test runs, the build failed with a Provisioning message:

error: Provisioning profile "..." doesn't include the currently selected device "..." (identifier ...).

This was resolved by manually selecting the target device:

A) Open the Xcode workspace:

open ./ios/SheetJSRNFetch.xcworkspace

B) Select the project in the left sidebar:

C) In the top bar, next to the project name, there will be a gray device icon. Click on the icon and select the real device from the list.

Local Files

React Native does not provide a native file picker or a method for reading and writing data from documents on the devices. A third-party library must be used.

Since React Native internals change between releases, libraries may only work with specific versions of React Native. Project documentation should be consulted before picking a library.

The following table lists tested file plugins. "OS" lists tested platforms ("A" for Android and "I" for iOS).

File system Plugin	File Picker Plugin	OS
react-native-file-access	react-native-document-picker	AI
react-native-blob-util	react-native-document-picker	AI
expo-file-system	expo-document-picker	AI

App Configuration

Due to privacy concerns, apps must request file access. There are special APIs for accessing data and are subject to change in future platform versions.

Technical Details (click to show)

iOS

iOS applications typically require two special settings in Info.plist:

• UIFileSharingEnabled⁸ allows users to use files written by the app. A special folder will appear in the "Files" app.

• LSSupportsOpeningDocumentsInPlace⁹ allows the app to open files without creating a local copy.

Both settings must be set to true:

Info.plist (add to file)

<plist version="1.0">
<dict>
  <key>UIFileSharingEnabled</key>
  <true/>
  <key>LSSupportsOpeningDocumentsInPlace</key>
  <true/>
  <key>CFBundleDevelopmentRegion</key>

Once the options are set, generated files are visible to users and can be shared with other apps including "Mail", "Messages", and "Numbers".

Android

Permissions and APIs have evolved over time. For broadest compatibility, the following permissions must be enabled in AndroidManifest.xml:

• READ_EXTERNAL_STORAGE and WRITE_EXTERNAL_STORAGE allow apps to access files outside of the app scope. These are required for scoped storage access.

• android:requestLegacyExternalStorage="true" enabled legacy behavior in some older releases.

The manifest is saved to android/app/src/main/AndroidManifest.xml:

android/app/src/main/AndroidManifest.xml (add highlighted lines)

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <application
      android:requestLegacyExternalStorage="true"
      android:name=".MainApplication"
      android:label="@string/app_name"
      android:icon="@mipmap/ic_launcher"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:allowBackup="false"
      android:theme="@style/AppTheme">

Depending on the Android API level, there are three strategies for writing files:

• In "legacy" mode (supported in API levels up to 29), files can be written to the user Downloads or Documents folder directly.

• Using the MediaStore API, files should be copied to a visible location.

• Using the "Storage Access Framework", the user grants access to a folder and the app uses SAF APIs to create files and write data.

RN File Picker

The "File Picker" library handles two platform-specific steps:

1. Show a view that allows users to select a file from their device

2. Copy the selected file to a location that can be read by the application

The following libraries have been tested:

react-native-document-picker

react-native-document-picker provides a pickSingle method for users to select one file.

The file plugins generally require the copyTo: "cachesDirectory" option:

import { pickSingle } from 'react-native-document-picker';

const f = await pickSingle({
  allowMultiSelection: false,
  copyTo: "cachesDirectory",
  mode: "open"
});
const path = f.fileCopyUri; // this path can be read by RN file plugins

expo-document-picker

expo-document-picker is a picker that works with other modules in the Expo ecosystem.

The getDocumentAsync method allows users to select a file. The Expo file plugin requires the copyToCacheDirectory option:

import * as DocumentPicker from 'expo-document-picker';

const result = await DocumentPicker.getDocumentAsync({
  copyToCacheDirectory: true,
  type: ['application/vnd.ms-excel', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet']
});
const path = result.assets[0].uri; // this path can be read by RN file plugins

RN File Plugins

The following libraries have been tested:

react-native-blob-util

react-native-blob-util is the continuation of other libraries that date back to 2016.

The ascii type returns an array of numbers corresponding to the raw bytes. A Uint8Array from the data is compatible with the buffer type.

Reading and Writing snippets (click to hide)

Reading Data

import * as XLSX from "xlsx";
import RNFetchBlob from 'react-native-blob-util';
const { readFile } = RNFetchBlob.fs;

const res = await readFile(path, 'ascii');
const wb = XLSX.read(new Uint8Array(res), {type:'buffer'});

On iOS, the URI from react-native-document-picker must be massaged:

import { pickSingle } from 'react-native-document-picker';
import RNFetchBlob from 'react-native-blob-util';
const { readFile, dirs: { DocumentDir } } = RNFetchBlob.fs;

const f = await pickSingle({
  // Instruct the document picker to copy file to Documents directory
  copyTo: "documentDirectory",
  allowMultiSelection: false, mode: "open" });
// `f.uri` is the original path and `f.fileCopyUri` is the path to the copy
let path = f.fileCopyUri;
// iOS workaround
if (Platform.OS === 'ios') path = path.replace(/^.*\/Documents\//, DDP + "/");

const res = await readFile(path, 'ascii');

Writing Data

import * as XLSX from "xlsx";
import RNFetchBlob from 'react-native-blob-util';
const { writeFile, readFile, dirs:{ DocumentDir } } = RNFetchBlob.fs;

const wbout = XLSX.write(wb, {type:'buffer', bookType:"xlsx"});
const file = DocumentDir + "/sheetjsw.xlsx";
const res = await writeFile(file, Array.from(wbout), 'ascii');

Sharing Files in Android

copyToMediaStore uses the MediaStore API to share files.

The file must be written to the device before using the MediaStore API!

// ... continuation of "writing data"
const { MediaCollection } = RNFetchBlob;

/* Copy to downloads directory (android) */
try {
  await MediaCollection.copyToMediaStore({
    parentFolder: "",
    mimeType: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
    name: "sheetjsw.xlsx"
  }, "Download", file);
} catch(e) {}

react-native-file-access

react-native-file-access is a filesystem API that uses modern iOS and Android development patterns.

The base64 encoding returns strings compatible with the base64 type:

Reading and Writing snippets (click to hide)

Reading Data

import * as XLSX from "xlsx";
import { FileSystem } from "react-native-file-access";

const b64 = await FileSystem.readFile(path, "base64");
/* b64 is a Base64 string */
const workbook = XLSX.read(b64, {type: "base64"});

Writing Data

import * as XLSX from "xlsx";
import { Dirs, FileSystem } from "react-native-file-access";
const DDP = Dirs.DocumentDir + "/";

const b64 = XLSX.write(workbook, {type:'base64', bookType:"xlsx"});
/* b64 is a Base64 string */
await FileSystem.writeFile(DDP + "sheetjs.xlsx", b64, "base64");

Sharing Files in Android

cpExternal uses the MediaStore API to share files.

The file must be written to the device before using the MediaStore API!

// ... continuation of "writing data"

/* Copy to downloads directory (android) */
try {
  await FileSystem.cpExternal(file, "sheetjsw.xlsx", "downloads");
} catch(e) {}

expo-file-system

expo-file-system is a filesystem API that works with other modules in the Expo ecosystem.

Some Expo APIs return URI that cannot be read with expo-file-system. This will manifest as an error:

Unsupported scheme for location '...'

The expo-document-picker snippet makes a local copy.

The EncodingType.Base64 encoding is compatible with base64 type.

Reading and Writing snippets (click to hide)

Reading Data

Calling FileSystem.readAsStringAsync with FileSystem.EncodingType.Base64 encoding returns a promise resolving to a string compatible with base64 type:

import * as XLSX from "xlsx";
import * as FileSystem from 'expo-file-system';

const b64 = await FileSystem.readAsStringAsync(uri, { encoding: FileSystem.EncodingType.Base64 });
const workbook = XLSX.read(b64, { type: "base64" });

Writing Data

The FileSystem.EncodingType.Base64 encoding accepts Base64 strings:

import * as XLSX from "xlsx";
import * as FileSystem from 'expo-file-system';

const b64 = XLSX.write(workbook, {type:'base64', bookType:"xlsx"});
/* b64 is a Base64 string */
await FileSystem.writeAsStringAsync(FileSystem.documentDirectory + "sheetjs.xlsx", b64, { encoding: FileSystem.EncodingType.Base64 });

Sharing Files in Android

StorageAccessFramework uses the "Storage Access Framework" to share files.

SAF API methods must be used to request permissions, make files and write data:

import * as XLSX from "xlsx";
import { documentDirectory, StorageAccessFramework } from 'expo-file-system';

const b64 = XLSX.write(workbook, {type:'base64', bookType:"xlsx"});
/* b64 is a Base64 string */
try {
  /* request access to a folder */
  const perms = await StorageAccessFramework.requestDirectoryPermissionsAsync(documentDirectory);
  /* if the user selected a folder ... */
  if(perms.granted) {

    /* create a new file */
    const uri = perms.directoryUri;
    const file = await StorageAccessFramework.createFileAsync(uri, "sheetjsw", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");

    /* write data to file */
    await StorageAccessFramework.writeAsStringAsync(file, wbout, { encoding: "base64" });
  }
} catch(e) {}

Demo

Tested Deployments

This demo was tested in the following environments:

Real Devices

OS	Device	RN	Date
iOS 15.5	iPhone 13 Pro Max	0.73.6	2024-03-31
Android 29	NVIDIA Shield	0.73.6	2024-03-31

Simulators

OS	Device	RN	Dev Platform	Date
Android 34	Pixel 3a	0.73.6	darwin-x64	2024-03-31
iOS 17.4	iPhone 15 Pro Max	0.73.6	darwin-x64	2024-03-31
Android 34	Pixel 3a	0.73.6	win10-x64	2024-03-31
Android 34	Pixel 3a	0.73.6	linux-x64	2024-03-31

There are many moving parts and pitfalls with React Native apps. It is strongly recommended to follow the official React Native tutorials for iOS and Android before approaching this demo.¹⁰ Details including Android Virtual Device configuration are not covered here.

This example tries to separate the library-specific functions.

Project Setup

1. Create project:

npx react-native init SheetJSRN --version="0.73.6"

On macOS, if prompted to install CocoaPods, press y.

2. Install shared dependencies:

cd SheetJSRN
curl -LO https://docs.sheetjs.com/logo.png
npm i -S https://cdn.sheetjs.com/xlsx-0.20.3/xlsx-0.20.3.tgz
npm i -S react-native-table-component@1.2.2 react-native-document-picker@9.1.1

3. Download index.js and replace:

curl -LO https://docs.sheetjs.com/mobile/index.js

4. Start the Android emulator:

npx react-native run-android

The app should look like the following screenshot:

When this demo was last tested on Windows, the build failed with an error:

> Failed to apply plugin 'com.android.internal.application'.
   > Android Gradle plugin requires Java 17 to run. You are currently using Java 11.

Java 17 must be installed¹¹ and the JAVA_HOME environment variable must point to the Java 17 location.

Stop the dev server and close the React Native Metro NodeJS window.

File Integration

5. Pick a filesystem library for integration:

RNBU

Install react-native-blob-util dependency:

npm i -S react-native-blob-util@0.19.8

Add the highlighted lines to index.js:

index.js

import { Table, Row, Rows, TableWrapper } from 'react-native-table-component';

import { read, write } from 'xlsx';
import { pickSingle } from 'react-native-document-picker';
import { Platform } from 'react-native';
import RNFetchBlob from 'react-native-blob-util';

async function pickAndParse() {
  const f = await pickSingle({allowMultiSelection: false, copyTo: "documentDirectory", mode: "open" });
  let path = f.fileCopyUri;
  if (Platform.OS === 'ios') path = path.replace(/^.*\/Documents\//, RNFetchBlob.fs.dirs.DocumentDir + "/");
  const res = await (await fetch(path)).arrayBuffer(); // RN >= 0.72
  // const res = await RNFetchBlob.fs.readFile(path, 'ascii'); // RN < 0.72
  return read(new Uint8Array(res), {type: 'buffer'});
}

async function writeWorkbook(wb) {
  const wbout = write(wb, {type:'buffer', bookType:"xlsx"});
  const file = RNFetchBlob.fs.dirs.DocumentDir + "/sheetjsw.xlsx";
  await RNFetchBlob.fs.writeFile(file, Array.from(wbout), 'ascii');

  /* Copy to downloads directory (android) */
  try { await RNFetchBlob.MediaCollection.copyToMediaStore({
    parentFolder: "",
    mimeType: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
    name: "sheetjsw.xlsx"
  }, "Download", file); } catch(e) {}

  return file;
}

const make_width = ws => {

RNFA

Install react-native-file-access dependency:

npm i -S react-native-file-access@3.0.7

Add the highlighted lines to index.js:

index.js

import { Table, Row, Rows, TableWrapper } from 'react-native-table-component';

import { read, write } from 'xlsx';
import { pickSingle } from 'react-native-document-picker';
import { Dirs, FileSystem } from 'react-native-file-access';

async function pickAndParse() {
  const f = await pickSingle({allowMultiSelection: false, copyTo: "documentDirectory", mode: "open" });
  let path = f.fileCopyUri;
  const res = await (await fetch(path)).arrayBuffer();
  return read(new Uint8Array(res), {type: 'buffer'});
}

async function writeWorkbook(wb) {
  const wbout = write(wb, {type:'base64', bookType:"xlsx"});
  const file = Dirs.DocumentDir + "/sheetjsw.xlsx";
  await FileSystem.writeFile(file, wbout, "base64");

  /* Copy to downloads directory (android) */
  try { await FileSystem.cpExternal(file, "sheetjsw.xlsx", "downloads"); } catch(e) {}

  return file;
}

const make_width = ws => {

EXPO

Install expo-file-system and expo-document-picker dependencies:

npx install-expo-modules
npm i -S expo-file-system expo-document-picker

In the most recent test, the installation asked a few questions.

If prompted to change iOS deployment target, choose Yes.

If prompted to install Expo CLI integration, choose No.

Add the highlighted lines to index.js:

index.js

import { Table, Row, Rows, TableWrapper } from 'react-native-table-component';

import { read, write } from 'xlsx';
import { getDocumentAsync } from 'expo-document-picker';
import { documentDirectory, readAsStringAsync, writeAsStringAsync, StorageAccessFramework } from 'expo-file-system';

async function pickAndParse() {
  const result = await getDocumentAsync({copyToCacheDirectory: true});
  const path = result.assets[0].uri;
  const res = await readAsStringAsync(path, { encoding: "base64" });
  return read(res, {type: 'base64'});
}

async function writeWorkbook(wb) {
  const wbout = write(wb, {type:'base64', bookType:"xlsx"});
  const file = documentDirectory + "sheetjsw.xlsx";
  await writeAsStringAsync(file, wbout, { encoding: "base64" });

  /* Write to documents directory (android) */
  try {
  const perms = await StorageAccessFramework.requestDirectoryPermissionsAsync(documentDirectory);
  if(perms.granted) {
    const uri = perms.directoryUri;
    const file = await StorageAccessFramework.createFileAsync(uri, "sheetjsw", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
    await StorageAccessFramework.writeAsStringAsync(file, wbout, { encoding: "base64" });
  }
  } catch(e) {}
  return file;
}

const make_width = ws => {

Android Testing

7. Restart the Android development process:

npx react-native run-android

The following app will be shown:

When this demo was last tested on macOS, the process failed to launch the emulator:

warn Please launch an emulator manually or connect a device. Otherwise app may fail to launch.

This is a known bug in React Native!

If an emulator is installed, run the following command:

npx react-native doctor

Under Android, there will be one error:

Android 

 ✖ Adb - No devices and/or emulators connected. Please create emulator with Android Studio or connect Android device.

Press f and a list of available emulators will be shown. Select the emulator (typically the last line) and press Enter.

✔ Select the device / emulator you want to use › Emulator Pixel_3a_API_34 (disconnected)

The text in green is the name of the virtual device (Pixel_3a_API_34 in this example). Run the following command to manually start the emulator:

$ANDROID_HOME/tools/emulator -avd Pixel_3a_API_34

(replace Pixel_3a_API_34 with the name of the virtual device)

To confirm React Native detects the emulator, run the following command again:

npx react-native doctor

8. Download https://docs.sheetjs.com/pres.numbers and open the Downloads folder.

9. Click and drag pres.numbers from the Downloads folder into the simulator.

10. Click "Import data" and look for pres.numbers.

If the file is not displayed, click the ≡ icon and click "Downloads".

11. Select pres.numbers.

The screen should refresh with new contents:

12. Click "Export data".

expo-file-system on Android will prompt to grant access to a folder.

Tap the ≡ icon and tap the "Documents" folder with the download icon.

Tap the 'ALLOW ACCESS TO "DOCUMENTS"' button.

In the "Allow access" pop, tap "ALLOW".

An alert will display the location to the file:

13. Pull the file from the simulator and verify the contents:

adb exec-out run-as com.sheetjsrn cat files/sheetjsw.xlsx > /tmp/sheetjsw.xlsx
npx xlsx-cli /tmp/sheetjsw.xlsx

PowerShell mangles binary data in the redirect.

On Windows, the following commands must be run in the Command Prompt:

adb exec-out run-as com.sheetjsrn cat files/sheetjsw.xlsx > sheetjsw.xlsx
npx xlsx-cli sheetjsw.xlsx

14. Stop the dev server and close the React Native Metro NodeJS window.

iOS Testing

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

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

Scroll down to "Android Device Testing" for device tests.

15. Refresh iOS project by running pod install from the ios subfolder:

cd ios; pod install; cd -

16. Start the iOS development process:

npx react-native run-ios

17. Download https://docs.sheetjs.com/pres.numbers and open the Downloads folder.

18. In the simulator, click the Home icon to return to the home screen.

19. Click on the "Files" icon to open the app.

20. Click and drag pres.numbers from the Downloads folder into the simulator.

21. Make sure "On My iPhone" is highlighted and select "Save".

22. Click the Home icon again then select the SheetJSRN app.

23. Click "Import data" and select pres:

Once selected, the screen should refresh with new contents:

24. Click "Export data".

An alert will display the location to the file:

25. Find the file and verify the contents are correct:

find ~/Library/Developer/CoreSimulator -name sheetjsw.xlsx |
  while read x; do echo "$x"; npx xlsx-cli "$x"; done

Once testing is complete, stop the simulator and the development process.

Android Device Testing

26. Add the highlighted lines to android/app/src/main/AndroidManifest.xml:

android/app/src/main/AndroidManifest.xml (add highlighted lines)

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <application
      android:requestLegacyExternalStorage="true"
      android:name=".MainApplication"
      android:label="@string/app_name"
      android:icon="@mipmap/ic_launcher"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:allowBackup="false"
      android:theme="@style/AppTheme">

There will be two new uses-permission tags within the parent manifest tag. The attribute android:requestLegacyExternalStorage="true" must be added to the application tag.

27. Close any Android / iOS simulators.

Stop the dev server and close the React Native Metro NodeJS window.

28. Connect an Android device using a USB cable.

If the device asks to allow USB debugging, tap "Allow".

29. Build APK and run on device:

npx react-native run-android

30. Download https://docs.sheetjs.com/pres.numbers on the device.

31. Switch back to the "SheetJSRN" app.

32. Tap "Import data" and tap pres.numbers.

If the file is not displayed, tap the ≡ icon and tap "Downloads".

The table will refresh with data from the file.

33. Tap "Export Data".

expo-file-system on Android will prompt to grant access to a folder.

Tap the ≡ icon and tap the "Documents" folder with the download icon.

Tap the 'ALLOW ACCESS TO "DOCUMENTS"' button.

In the "Allow access" pop, tap "ALLOW".

Tap "OK" in the exportFile popup.

34. Switch to the Files app and navigate to the Downloads folder.

When testing expo-file-system, select "Documents".

There will be a new file sheetjsw.xlsx.

35. Close and reopen the "SheetJSRN" app. The data will reset.

36. Tap "Import data" and tap sheetjsw.xlsx.

If the file is not displayed, tap the ≡ icon and tap "Downloads".

When testing expo-file-system, select "Documents".

The table will refresh with the data from the exported file.

iOS Device Testing

37. Close any Android / iOS emulators.

38. Enable file sharing and make the documents folder visible in the iOS app. Add the following lines to ios/SheetJSRN/Info.plist:

ios/SheetJSRN/Info.plist (add to file)

<plist version="1.0">
<dict>
  <key>UIFileSharingEnabled</key>
  <true/>
  <key>LSSupportsOpeningDocumentsInPlace</key>
  <true/>
  <key>CFBundleDevelopmentRegion</key>

(The root element of the document is plist and it contains one dict child)

39. Enable developer code signing certificates. More details are covered in the "iOS Device Testing" part of the Fetch Demo (step 15).

40. Install ios-deploy through Homebrew:

brew install ios-deploy

41. Run on device:

npx react-native run-ios

If the build fails, some troubleshooting notes are included in the "iOS Device Testing" part of the Fetch Demo (step 17).

41. Download https://docs.sheetjs.com/pres.numbers on the device.

42. Switch back to the "SheetJSRN" app.

43. Tap "Import data" and tap pres from the Recents list.

The table will refresh with data from the file.

44. Tap "Export Data" and tap "OK" in the exportFile popup.

45. Install the "Numbers" app from the iOS App Store.

46. Open the "Files" app. Repeatedly tap the < button in the top-left corner to return to the "Browse" view.

47. Tap "On My iPhone" or "On My iPad". Tap "SheetJSRN" in the list.

The sheetjsw entry in this folder is the generated file.

48. Hold down the sheetjsw item until the menu appears. Select "Share".

49. In the sharing menu, below a list of contacts, there will be a row of app icons. Swipe left until the "Numbers" app icon appears and tap the app icon.

The Numbers app will load the spreadsheet, confirming that the file is valid.

Footnotes

1. Follow the "React Native CLI Quickstart" and select the appropriate "Development OS". ↩

2. See "Array of Arrays" in the API reference ↩

3. See "Array Output" in "Utility Functions" ↩

4. See "Array of Arrays Input" in "Utility Functions" ↩

5. React-Native commit 5b597b5 added the final piece required for fetch support. It is available in official releases starting from 0.72.0. ↩

6. When the demo was last tested, the Temurin distribution of Java 17 was installed through the macOS Brew package manager by running brew install temurin17. Direct downloads are available at adoptium.net ↩

7. See "Running On Device" in the React Native documentation ↩

8. See UIFileSharingEnabled in the Apple Developer Documentation. ↩

9. See LSSupportsOpeningDocumentsInPlace in the Apple Developer Documentation. ↩

10. Follow the "React Native CLI Quickstart" for Android (and iOS, if applicable) ↩

11. See the JDK Archive for Java 17 JDK download links. ↩