React-native-fs sample code to implement file download and text storage

npm install react-native-fs --save

react-native link react-native-fs

import RNFS from 'react-native-fs';

/*Download file*/
  downloadFile() {
    // On Android, use "" (MainBundlePath is not defined)

    // picture    // const downloadDest = `${}/${((() * 1000) | 0)}.jpg`;
    // const formUrl = '/?imageMogr2/quality/60/format/jpg';

    // document    // const downloadDest = `${}/${((() * 1000) | 0)}.zip`;
    // const formUrl = '/zhuqil/';

    // video    // const downloadDest = `${}/${((() * 1000) | 0)}.mp4`;
    // /stream/SnY~bbkqbi2uLEBMXHxGqnNKqyiG9ub8.mp4?vend=miaopai&
    // /stream/BNaEYOL-tEwSrAiYBnPDR03dDlFavoWD.mp4?vend=miaopai&
    // const formUrl = '/stream/9Q5ADAp2v5NHtQIeQT7t461VkNPxvC2T.mp4?vend=miaopai&';

    // Audio    const downloadDest = `${}/${((() * 1000) | 0)}.mp3`;
    // /voice/2015/0902/55e6fc6e4f7b9.mp3
    const formUrl = '/voice/2015/0818/55d2248309b09.mp3';

    const options = {
      fromUrl: formUrl,
      toFile: downloadDest,
      background: true,
      begin: (res) => {
        ('begin', res);
        ('contentLength:',  / 1024 / 1024, 'M');
      },
      progress: (res) => {

        let pro =  / ;

        ({
          progressNum: pro,
        });
      }
    };
    try {
      const ret = (options);
      (res => {
        ('success', res);

        ('file://' + downloadDest)

      }).catch(err => {
        ('err', err);
      });
    }
    catch (e) {
      (error);
    }

  }

 /*Write text to local txt*/
  writeFile() {
    // create a path you want to write to
    const path =  + '/';

    // write the file
    (path, 'This is a piece of text, YES', 'utf8')
      .then((success) => {
        ('path', path);
      })
      .catch((err) => {
        ();
      });
  }

/*Read the content of the txt file*/
  readFile() {
    // create a path you want to delete
    const path =  + '/';

    return (path)
      .then((result) => {
        (result);

        ({
          readTxtResult: result,
        })
      })
      .catch((err) => {
        ();

      });
  }

/*Add new text on existing txt*/
  appendFile() {
    const path =  + '/';

    return (path, 'Newly added text', 'utf8')
      .then((success) => {
        ('success');
      })
      .catch((err) => {
        ();

      });
  }

  /*Delete file*/
  deleteFile() {
    // create a path you want to delete
    const path =  + '/';

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

 /*Upload file only iOS*/
  uploadFile() {
    const uploadSrc = `${}/`;

    const uploadUrl = '/rnfs/';

    const options = {
      toUrl: uploadUrl,
      files: [{name: 'myfile', filename: '', filepath: uploadSrc, filetype: 'text/plain'}],
      background: true,
      method: 'POST', // PUT
      begin: (res) => {
        ('begin', res);
      },
      progress: (res) => {
        ('progress', res);
      }
    };

    const ret = (options);

    return (res => {
      const response = ();
      (response);

    })
      .catch(err => {
        ('err', err);
      });
  }