remove item with callback

remove-item-api.ts

private removeItem(item: Item) {
       
       let index = this.items.indexOf(item);
       //remove the item
       this.items.splice(index, 1);
       
       //call back-end server to remove the item from the DB
        this.itemService.deleteItem(item.id).subscribe(
            //do some stuff
            ,
            error => {
            //in case of error, add the callback to bring the item back and re-throw the error.
              error.callback=()=>this.items.splice(index, 0, item);
              throw error;
            }
        );
    }