DefinitelyTyped/types/react-native-fs/react-native-fs-tests.ts

import * as RNFS from 'react-native-fs';

// get a list of files and directories in the main bundle
RNFS.readDir(RNFS.MainBundlePath) // On Android, use "RNFS.DocumentDirectoryPath" (MainBundlePath is not defined)
  .then((result) => {
    console.log('GOT RESULT', result);

    // stat the first file
    return Promise.all([RNFS.stat(result[0].path), result[0].path]);
  })
  .then((statResult) => {
    if (statResult[0].isFile()) {
      // if we have a file, read it
      return RNFS.readFile(statResult[1], 'utf8');
    }

    return 'no file';
  })
  .then((contents) => {
    // log the file contents
    console.log(contents);
  })
  .catch((err) => {
    console.log(err.message, err.code);
  });

// create a path you want to write to
const path = RNFS.DocumentDirectoryPath + '/test.txt';

// write the file
RNFS.writeFile(path, 'Lorem ipsum dolor sit amet', 'utf8')
  .then(() => {
    console.log('FILE WRITTEN!');
  })
  .catch((err) => {
    console.log(err.message);
  });

RNFS.unlink('path')
  .then(() => {
    console.log('FILE DELETED');
  })
  // `unlink` will throw an error, if the item to unlink does not exist
  .catch((err) => {
    console.log(err.message);
  });

const uploadUrl = 'http://requestb.in/XXXXXXX';  // For testing purposes, go to http://requestb.in/ and create your own link
// create an array of objects of the files you want to upload
const files = [
  {
    name: 'test1',
    filename: 'test1.w4a',
    filepath: RNFS.DocumentDirectoryPath + '/test1.w4a',
    filetype: 'audio/x-m4a'
  }, {
    name: 'test2',
    filename: 'test2.w4a',
    filepath: RNFS.DocumentDirectoryPath + '/test2.w4a',
    filetype: 'audio/x-m4a'
  }
];

const uploadBegin: RNFS.UploadCallbackBegin = (response) => {
  const jobId = response.jobId;
  console.log('UPLOAD HAS BEGUN! JobId: ' + jobId);
};

const uploadProgress: RNFS.UploadCallbackProgress = (response) => {
  const percentage = Math.floor((response.totalBytesSent / response.totalBytesExpectedToSend) * 100);
  console.log(`UPLOAD IS ${percentage}% DONE!`);
};

// upload files
RNFS.uploadFiles({
  toUrl: uploadUrl,
  files,
  method: 'POST',
  headers: {
    Accept: 'application/json',
  },
  fields: {
    hello: 'world',
  },
  begin: uploadBegin,
  progress: uploadProgress
}).promise.then((response) => {
    if (response.statusCode === 200) {
      console.log('FILES UPLOADED!'); // response.statusCode, response.headers, response.body
    } else {
      console.log('SERVER ERROR');
    }
  })
  .catch((err) => {
    if (err.description === "cancelled") {
      // cancelled by user
    }
    console.log(err);
  });

const downloadProgress: RNFS.DownloadCallbackProgress = (result) => {
  result.bytesWritten === 0;
  result.contentLength > 10;
  result.jobId;
};

const downloadBegin: RNFS.DownloadCallbackBegin = (result) => {
  result.headers === {};
};

RNFS.downloadFile({
  fromUrl: 'http://.txt',
  toFile: 'file.txt',
  begin: downloadBegin,
  progress: downloadProgress
}).promise.then((response) => {
  response.statusCode === 200;
});