Angular / Typescript Promise Resolver

velvet-resolver.ts

purchaseOrderIds = ['12345', '67890'];

getPurchaseOrderDetails() {
  const promises = [];
    this.purchaseOrderIds.map(x => {
      promises.push(new Promise((resolve) => {
        this.purchaseOrderService.getPurchaseOrder(x)
          .subscribe(
            res => {
              resolve(res);
            },
            err => {
              console.error('error getting', x);
              resolve(err);
            }
          );
      }));
    });
    Promise.all(promises).then((completed) => {
      this.purchaseOrderIds = completed;
    });
}