1. 查看当前react native的版本号
react-native --version
2. 查看最新react native库版本
npm info react-native
3. 升级
npm install --save react-native@0.65.1
3. 降级
npm install --save react-native@0.51.1
react-native --version
npm info react-native
npm install --save react-native@0.65.1
npm install --save react-native@0.51.1