需要輸出的類

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

var Dimensions = require('Dimensions');
//獲取螢幕寬度
var screenWidth = Dimensions.get('window').width;

export default class loginView extends Component {
    render() {
        return
 
 (
                    <View>
                      <Text>輸出</Text>  
                  </View>
        );
    }
}

//輸出一個類
module.exports = loginView;

接收檔案的js檔案

import React, { Component } from 'react';
import {
    AppRegistry,
    StyleSheet,
    Text,
    View,

} from 'react-native'
 
;

//引入外部js注意首字母必須大寫
var LoginView = require('./loginModule/iOS/loginView');

export default class B2B extends Component {
  render() {
    return (
        <LoginView/>
    );
  }
}

AppRegistry.registerComponent('B2B', () => B2B);