我在windows 10上安装了nodejs v12.16.2，以使用react native进行学习，因此无需安装android studio或xocde。正如我在react native文档中所读到的，最简单的方法是使用expo-cli，我使用以下命令将其安装在我的机器上，但它不起作用：
$ npm install -g expo-cli
$ npm install expo-cli --global
$ yarn add global expo-cli
所有这些命令最终都会出现错误，我错过了什么，以及如何解决这个问题。以下是问题的详细信息：
npm install expo-cli --global npm WARN deprecated joi@14.0.4: This version has been deprecated in accordance with the hapi support policy (hapi.im/support). Please upgrade to the latest version to get the best features, bug fixes, and security patches. If you are unable to upgrade at this time, paid support is available for older versions (hapi.im/commercial).
npm WARN deprecated request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/traveling-fastlane-darwin@1.13.1 (node_modulesexpo-clinode_modules@expotraveling-fastlane-darwin):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/traveling-fastlane-darwin@1.13.1: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-freebsd-x64@2.2.8 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-freebsd-x64):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-freebsd-x64@2.2.8: wanted {"os":"freebsd","arch":"x64"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-darwin-ia32@2.2.8 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-darwin-ia32):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-darwin-ia32@2.2.8: wanted {"os":"darwin","arch":"ia32"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-darwin-x64@2.2.8 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-darwin-x64):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-darwin-x64@2.2.8: wanted {"os":"darwin","arch":"x64"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-freebsd-ia32@2.2.8 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-freebsd-ia32):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-freebsd-ia32@2.2.8: wanted {"os":"freebsd","arch":"ia32"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-linux-arm64@2.2.8 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-linux-arm64):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-linux-arm64@2.2.8: wanted {"os":"linux","arch":"arm64"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-linux-ia32@2.2.8 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-linux-ia32):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-linux-ia32@2.2.8: wanted {"os":"linux","arch":"ia32"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-linux-arm@2.2.8 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-linux-arm):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-linux-arm@2.2.8: wanted {"os":"linux","arch":"arm"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-sunos-x64@2.2.8 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-sunos-x64):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-sunos-x64@2.2.8: wanted {"os":"sunos","arch":"x64"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-linux-x64@2.2.8 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-linux-x64):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-linux-x64@2.2.8: wanted {"os":"linux","arch":"x64"} (current: {"os":"win32","arch":"ia32"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: @expo/ngrok-bin-win32-x64@2.2.8-beta.1 (node_modulesexpo-clinode_modules@expongrok-binnode_modules@expongrok-bin-win32-x64):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for @expo/ngrok-bin-win32-x64@2.2.8-beta.1: wanted {"os":"win32","arch":"x64"} (current: {"os":"win32","arch":"ia32"})
npm ERR! Unexpected end of JSON input while parsing near '...in-proposal-unicode-p'
由于使用npm中的optionalDependencies来安装适用于您的平台的ngrok包，因此您看到的警告是不可避免的，因此不要担心。与您相关的错误是"npm ERR！解析附近时JSON输入意外结束…"-有很多关于这个主题的相关帖子，他们通常建议您执行以下操作：
- 清除npm缓存
npm cache clean --force - 再次运行安装
npm i -g expo-cli
请参阅https://stackoverflow.com/a/47896884/659988以不同包的类似问题为例。