ERROR in node_modules/@ionic-native/in-app-browser/index.d.ts(2,10): error TS2305: Module ‘XXXXXXXXXXXXXXXXXXX/node_modules/rxjs/Observable”‘ has no exported member ‘Observable’.XXXXXXXXXXXXXXXnode_modules/rxjs/Observable”‘ has no exported member ‘Observable’.
node_modules/rxjs/Observable.d.ts(1,15): error TS2307: Cannot find module ‘rxjs-compat/Observable’.

解決策
 npm install rxjs@6 rxjs-compat@6 –save