Method finally

packages/zone.js/lib/common/promise.ts:560–575

(onFinally?: () => U | PromiseLike<U>)

      }

      finally<U>(onFinally?: () => U | PromiseLike<U>): Promise<R> {
        // See comment on the call to `then` about why thee `Symbol.species` is safely accessed.
        let C = (this.constructor as any)?.[Symbol.species];
        if (!C || typeof C !== 'function') {
          C = ZoneAwarePromise;
        }
        const chainPromise: Promise<R | never> = new (C as typeof ZoneAwarePromise)(noop);
        (chainPromise as any)[symbolFinally] = symbolFinally;
        const zone = Zone.current;
        if ((this as any)[symbolState] == UNRESOLVED) {
          (<any[]>(this as any)[symbolValue]).push(zone, chainPromise, onFinally, onFinally);
        } else {
          scheduleResolveOrReject(this, zone, chainPromise as any, onFinally, onFinally);
        }
        return chainPromise;
      }
    }
    // Protect against aggressive optimizers dropping seemingly unused properties.
    // E.g. Closure Compiler in advanced mode.