this snippet code should throw an error

download.js

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 * @flow
 */

import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  TextInput,
  TouchableOpacity
} from 'react-native'

import RNFetchBlob from 'react-native-fetch-blob'

export default class blob extends Component {

  constructor(props) {
    super(props);
    this.state = {
      url: '',
      received: 0,
      total: 0,
      path: null
    }
  }

  download = () => {
    const {url} = this.state
    const filename = 'small.mp4'
    const path = RNFetchBlob.fs.dirs.DocumentDir + '/' + filename

    console.log(url, path)
    RNFetchBlob
    .config({
      addAdnroidDownloads: {
        useDownloadManager: true,
        notification: true,
        description: filename,
        meidaScannable: true
      },
      fileCache : true,
      path
    })
    .fetch('GET', url)
    .progress({ interval: 1000 }, (received, total) => {
      this.setState({received, total})
    })
    .then((res) => {
      this.setState({
        path: res.path()
      })
    }, e => {
      console.log(e)
    })
  }

  openfile = () => {
    RNFetchBlob.ios.openDocument(this.state.path).then(r => r, e => e)
  }

  render() {
    return (
      <View style={styles.container}>
        <TextInput
          value={this.state.url}
          onChangeText={(url) => this.setState({url})}
          placeholder='enter url'
          style={{ width: 300, height: 30 }} />

        <TouchableOpacity onPress={this.download}>
          <Text>Download</Text>
        </TouchableOpacity>

        <Text style={{ marginTop: 40 }}>{ this.state.received } / { this.state.total} </Text>

        {
          this.state.path != null &&
          <View style={{ marginTop: 40 }}>
            <TouchableOpacity onPress={this.openfile}>
              <Text>Open { this.state.path }</Text>
            </TouchableOpacity>
          </View>
        }
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    marginTop: 100,
  }
});

AppRegistry.registerComponent('blob', () => blob);