How to use the react-native-fs.DocumentDirectoryPath function in react-native-fs

import React from 'react'

import fs from 'react-native-fs'
import ImageViewer from 'react-native-image-zoom-viewer'
import {
  Animated,
  Easing,
  CameraRoll
} from 'react-native'

declare var global

const psnineFolder = fs.DocumentDirectoryPath + '/psnine'

fs.stat(psnineFolder).then(data => {
  const isDirectory = data.isDirectory()
  if (!isDirectory) {
    fs.unlink(psnineFolder).catch(() => {}).then(() => fs.mkdir(psnineFolder))
  }
}).catch(() => {
  fs.mkdir(psnineFolder).catch(err => console.log(err, 'ImageViewer:line#27'))
})

const onSave = (image) => {
  // console.log(image, psnineFolder + '/' + image.split('/').pop())
  const result = CameraRoll.saveToCameraRoll(image)
  return result.then((url) => {
    global.toast('保存成功')
    return url

export default async function photosTask (dispatch, failedImages) {
  // console.log('FAILED IMAGES:', failedImages)
  console.log('running photos task')
  BackgroundTimer.start() // This requests some background time from the OS

  // Start IPFS
  const path = RNFS.DocumentDirectoryPath
  await IPFS.createNodeWithDataDir(path)
  await IPFS.startNode()

  // Get a list of the jobs already in the queue
  // const existingJobs = await queue.getJobs(true)

  // Query for any new photos, add jobs to queue
  const photos = await queryPhotos()
  // PushNotificationIOS.presentLocalNotification({
  //   alertBody: 'fetch of ' + photos.length + ' photos',
  //   userInfo: {}
  // })
  for (const photo of photos) {
    const multipartData = await IPFS.addImageAtPath(photo.node.image.path, photo.node.image.thumbPath)
    await RNFS.unlink(photo.node.image.path)
    await RNFS.unlink(photo.node.image.thumbPath)

const getRootDir = () => {
	switch (Platform.OS) {
		case 'ios': // Check GoBridge.swift
		case 'android': // Check GoBridgeModule.java
			return RNFS.DocumentDirectoryPath + '/berty'

		default:
			throw new Error('unsupported platform')
	}
}

export function * parseNewCode(action: ActionType) {
  const appThread = yield select(MainSelectors.getAppThread)

  const url = parseUrl(action.payload.url, true)
  const label = url.pathname.slice(1).split(':')
  const file = url.query
  file['user'] = label[1]
  file['type'] = url.host

  const path = RNFS.DocumentDirectoryPath + '/' + fakeUUID() + '.json'
  try {
   yield call(RNFS.writeFile, path, JSON.stringify(file), 'utf8')
   const result = yield call(Textile.prepareFilesAsync, path, appThread.id)
   yield call(RNFS.unlink, path)

   const dir = result.dir
   if (!dir) {
     return
   }
   yield call(Textile.addThreadFiles, dir, appThread.id)
   yield call(refreshThreads, appThread)
  } catch (err) {
    console.log("CODY ERR: " + err.message)
  }
}

static async getBinaryAttachment() {
    const path = `${RNFS.DocumentDirectoryPath}/${BINARY_ATTACHMENT_STORAGE_FILENAME}`;
    let contents = '';
    try {
      contents = await RNFS.readFile(path, DEFAULT_ENCODING);
    } catch (error) {
      console.log(`Error while reading binary attachment file, error: ${error}`);
    }
    return contents;
  }

render() {
    const { photo, name, score, connectionDate, style } = this.props;

    return (

async function moveTextileFiles() {
  const files = await RNFS.readDir(RNFS.DocumentDirectoryPath)
  for (const file of files) {
    if (file.path !== REPO_PATH && file.name !== 'RCTAsyncLocalStorage_V1') {
      await RNFS.moveFile(file.path, `${REPO_PATH}/${file.name}`)
    }
  }
}

svg.toDataURL(async (data: string) => {
    const path = RNFS.DocumentDirectoryPath + QRFileName
    try {
      await RNFS.writeFile(path, data, 'base64')
      Share.open({
        url: 'file://' + path,
        type: 'image/png',
      }).catch((err: Error) => {
        throw err
      })
    } catch (e) {
      Logger.warn(TAG, e)
    }
  })
}