Typescript和rxjs 6-类型'{}'不存在该属性

Question

I'm developing a small app with Ionic 3 querying a firebase db to get 2 series of data. The first build fail with error "Property does not exist on type '{}'" but if I save one more time the .ts file (save for ex. home.ts so that ionic rebuild) the error disappear and the page works.

I'm doing:

ionViewDidLoad() {

  this.db.list('myPath-in-firebase', ref => ref.orderByChild('my-key'))
    .valueChanges()
      .subscribe(result => { 
      let mydata1= result.map(x => x.my-property-key1);
      let mydata2= result.map(x => x.my-property-key2);
      console.log(mydata1);
      };
}

but I get a typescript error: "Property 'my-property-key1' does not exist on type '{}'" in the first ionic serve build start, then I save a file of the project, ionic rebuild and it works fine. I guess that I have to declare x and his properties somewhere but I cannot know how and where.

Finally (maybe there is a better method and you could help me?), my DB is like so:

my-firebase-database
    |- my-Path
           |- Push-ID-1
                   |- my-property-key1: value
                   |- my-property-key2: value
           |- Push-ID-2
                   |- my-property-key1: value
                   |- my-property-key2: value
           |- Push-ID-3
                   |- my-property-key1: value
                   |- my-property-key2: value

I would have 2 array, one containing values of my-property-key1 and the other with my-property-key2 values. Thanks for helping

Update : See in comments. At the moment I was using a workaround changing syntax from result.map(x => x.my-property-key1) to result.map(x => x[my-property-key1])

according to this: https://github.com/Microsoft/TypeScript/issues/12596

Answer 1

Try

npm remove --save typescript;
npm i --save-dev typescript@2.6.2;
npm i --save-dev rxjs@6.2.2
npm i --save-dev rxjs-compat@6.2.2



import 'rxjs/Rx';

import { switchMap, map } from 'rxjs/operators';
import { Observable, pipe } from 'rxjs';