import { ThemeDetection } from '@awesome-cordova-plugins/theme-detection';
constructor(private themeDetection: ThemeDetection) { }
...
this.themeDetection.isAvailable()
  .then((res: ThemeDetectionResponse) => {
     if(res.value) {
       this.themeDetection.isDarkModeEnabled().then((res: ThemeDetectionResponse) => {
         console.log(res);
       })
       .catch((error: any) => console.error(error));
     }
  })
  .catch((error: any) => console.error(error));