doRefresh(refresher?) {

let d = get_data();

 if (d == "d"){
    refresher.complete();
  }else{
    console.log('value is not d')
    refresher.complete()
  }
}

ionViewDidLoad(){
  this.doRefresh();
}

<ion-refresher (ionRefresh)="doRefresh($event);">
   <ion-refresher-content
      pullingText="Pull to refresh" pullingIcon="arrow-dropdown"
      refreshingSpinner="circles"
   refreshingText="..fetching">
   </ion-refresher-content>
   </ion-refresher>