data: BaseData[] = [];


initData() {
 this.dataProvider.getData()
.subscribe(this.addNewData());
}

initData() {
 this.dataProvider.getData()
.subscribe(
          data => {
            this.addNewData();
            this.showProgressSpinner = false;
            console.log(this.data);
          });
    }
}

  private addNewData() {
    const dataIds = this.data.map(i => i.dataId);
    return fetchedData => fetchedData
      .filter(i => ! dataIds.includes(i.dataId))
      .forEach(i => this.data.push(i));
  }