npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for [email protected]: want

D:\ionic_demo\demo4>   npm uninstall -D @ionic/cli-plugin-ionic-angular
npm WARN @ionic-native/[email protected] requires a peer of @ionic-native/core@^4.11.0 but none is installed. You must install peer dependencies yourself.
npm WARN @ionic-native/[email protected] requires a peer of @ionic-native/core@^4.11.0 but none is installed. You must install peer dependencies yourself.
npm WARN @ionic-native/[email protected] requires a peer of @ionic-native/core@^4.11.0 but none is installed. You must install peer dependencies yourself.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: [email protected] (node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for [email protected]: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
 

原因:fsevents不在package.json里，但是仍然安装了，是因为你的系统不是Windows系统，fsevents是苹果系统的可选依赖,你的项目有可能是团队项目，别人在他的mac上安装了fsevents相关依赖库，所以到这边你也就安装到你的windows上边了。你可以检查你的package.json 文件中是不是有fsevents相关依赖，删除即好！ 
如果没有，删除node_modules文件夹，重新安装各项依赖就好了

解决:fsevent是mac osx系统的，你是在win或者Linux下使用了 所以会有警告，忽略即可