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React Native

The NodeJS Module can be imported from the main App.js entrypoint or any script in the project.

The "Complete Example" creates an app that looks like the screenshots below:

iOSAndroid

iOS screenshot

Android screenshot

Native Libraries

danger

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). "Copy" indicates whether an explicit copy is needed (file picker copies to cache directory and file plugin reads cache).

File system PluginFile Picker PluginOSCopy
react-native-file-accessreact-native-document-pickerAI
react-native-blob-utilreact-native-document-pickerAIYES
rn-fetch-blobreact-native-document-pickerAIYES
react-native-fsreact-native-document-pickerAIYES
expo-file-systemexpo-document-picker IYES

RN File Picker

The following libraries have been tested:

react-native-document-picker

Selecting a file (click to show)

When a copy is not needed:

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

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

When a copy is needed:

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

Selecting a file (click to show)

When using DocumentPicker.getDocumentAsync, enable copyToCacheDirectory:

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.uri;

RN File Plugins

The following libraries have been tested:

react-native-blob-util and rn-fetch-blob

Historical Context

The react-native-fetch-blob project was archived in 2019. At the time, there were a number of project forks. The maintainers blessed the rn-fetch-blob fork as the spiritual successor.

react-native-blob-util is an active fork of rn-fetch-blob

On the day that this demo was tested (2022 August 14), both rn-fetch-blob and react-native-blob-util worked with the tested iOS and Android SDK versions. The APIs are identical for the purposes of working with files.

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 show)

The snippets use rn-fetch-blob. To use react-native-blob-util, change the import statements to load the module.

Reading Data

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

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

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

import { pickSingle } from 'react-native-document-picker';
import RNFetchBlob from 'rn-fetch-blob'; // or 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 'rn-fetch-blob'; // or 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');

react-native-file-access

The base64 encoding returns strings compatible with the base64 type:

Reading and Writing snippets (click to show)

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");

react-native-fs

The ascii encoding returns binary strings compatible with the binary type:

Reading and Writing snippets (click to show)

Reading Data

import * as XLSX from "xlsx";
import { readFile } from "react-native-fs";

const bstr = await readFile(path, "ascii");
/* bstr is a binary string */
const workbook = XLSX.read(bstr, {type: "binary"});

Writing Data

import * as XLSX from "xlsx";
import { writeFile, DocumentDirectoryPath } from "react-native-fs";

const bstr = XLSX.write(workbook, {type:'binary', bookType:"xlsx"});
/* bstr is a binary string */
await writeFile(DocumentDirectoryPath + "/sheetjs.xlsx", bstr, "ascii");

expo-file-system

caution

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 show)

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 });

Demo

note

This demo was tested on an Intel Mac on 2022 August 14 with RN 0.67.2.

The iOS simulator runs iOS 15.5 on an iPhone 13.

The Android simulator runs Android 12 (S) Platform 31 on a Pixel 5.

danger

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. Details like creating an Android Virtual Device are not covered here.

This example tries to separate the library-specific functions.

0) Follow the official React Native CLI Guide!

Development Environment Guide: https://reactnative.dev/docs/environment-setup

Follow the instructions for iOS and for Android. They will cover installation and system configuration. By the end, you should be able to run the sample app in the Android and the iOS simulators.

1) Create project:

npx react-native init SheetJSRN --version="0.67.2"

2) Install shared dependencies:

cd SheetJSRN
curl -LO https://oss.sheetjs.com/assets/img/logo.png
npm i -S https://cdn.sheetjs.com/xlsx-latest/xlsx-latest.tgz
npm i -S react-native-table-component react-native-document-picker

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

cd ios
pod install
cd ..

3) Download index.js and replace:

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

Start the iOS emulator:

npx react-native run-ios

You should see the skeleton app:

React Native iOS App

4) Pick a filesystem library for integration:

Install react-native-blob-util dependency:

npm i -S react-native-blob-util

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() {
/* rn-fetch-blob / react-native-blob-util need a copy */
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 RNFetchBlob.fs.readFile(path, 'ascii');
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');
return file;
}

const make_width = ws => {

5) Refresh the app:

cd ios
pod install
cd ..

Once refreshed, the development process must be restarted:

npx react-native run-ios

iOS Testing

The app can be tested with the following sequence in the simulator:

  • Download https://sheetjs.com/pres.numbers
  • In the simulator, click the Home icon to return to the home screen
  • Click on the "Files" icon
  • Click and drag pres.numbers from a Finder window into the simulator.

save file iOS

  • Make sure "On My iPhone" is highlighted and select "Save"
  • Click the Home icon again then select the SheetJSRN app
  • Click "Import data" and select pres:

pick file iOS

Once selected, the screen should refresh with new contents:

read file iOS

  • Click "Export data". You will see a popup with a location:

write file iOS

  • 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 Testing

There are no Android-specific steps. Emulator can be started with:

npx react-native run-android

React Native Android App

The app can be tested with the following sequence in the simulator:

pick file Android

Once selected, the screen should refresh with new contents:

read file Android

  • Click "Export data". You will see a popup with a location:

write file Android

  • 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