如何通过脚本切换App.js文件运行React Native项目？

当然可行，不用手动改注释，通过环境变量+自定义脚本就能搞定，步骤如下：

1. 修改index.js，用环境变量动态选择入口 #

把原来的index.js改成根据环境变量加载对应App文件：

import { AppRegistry } from 'react-native'

// 读取环境变量，默认用App.js
const targetApp = process.env.APP_TARGET || 'App'
const myApp = require(`./src/${targetApp}`).default

AppRegistry.registerComponent('Dummy app', () => myApp)

2. 在package.json里添加自定义脚本 #

为了兼容Windows、macOS、Linux，推荐先装个cross-env包统一环境变量设置方式：

npm install cross-env --save-dev

然后在package.json的scripts字段里添加这些命令：

"scripts": {
  "start": "react-native start",
  "start:app2": "cross-env APP_TARGET=App2 react-native start",
  "android": "react-native run-android",
  "android:app2": "cross-env APP_TARGET=App2 react-native run-android",
  "ios": "react-native run-ios",
  "ios:app2": "cross-env APP_TARGET=App2 react-native run-ios"
}

如果不想额外装包，也可以针对不同系统写脚本：

• 对于macOS/Linux：

"start:app2": "APP_TARGET=App2 react-native start",
"android:app2": "APP_TARGET=App2 react-native run-android",
"ios:app2": "APP_TARGET=App2 react-native run-ios"

• 对于Windows（CMD命令行）：

"start:app2": "set APP_TARGET=App2 && react-native start",
"android:app2": "set APP_TARGET=App2 && react-native run-android",
"ios:app2": "set APP_TARGET=App2 && react-native run-ios"

3. 运行方式 #

要启动App2对应的项目，直接执行：

# 先启动metro
npm run start:app2
# 再打开对应平台（比如安卓）
npm run android:app2

内容的提问来源于stack exchange，提问作者Andy