javascript - 如何获取响应 header - 获取响应 header 的问题

Question

我在响应 header 中传递分页信息，但无法在 Angular 8 中使用以下方法。我一直收到 0 但响应显示不同的值。谁能告诉我我哪里出错了？

app.service.ts

  indexBooking(perPage: number, page: number) {
    return this.http
      .get<any[]>(`${this.apiBaseUrl}/prices`, {
        params: formatParameters({perPage, page}),
        observe: 'response',
      })
      .pipe(
        map((res) => ({
          max: Number.parseInt(res.headers.get('x-total-count'), 10) || 0,
          index: Number.parseInt(res.headers.get('x-next-page'), 10) || 0,
          page: Number.parseInt(res.headers.get('x-per-page'), 10) || 20,
          items: res.body,
        })),
      );
  }

app.component.ts

ngAfterViewInit() {
  merge(this.paginator.page)
    .pipe(
      startWith({}),
      switchMap(() => {
        return this.bookingService.indexBooking(this.paginator.pageSize, this.paginator.pageIndex);
      }),
      map((data) => {
        console.log('data', data);
        this.resultsLength = data.items.length;
        return data.items;
      }),
      catchError(() => {
        return observableOf([]);
      }),
    )
    .subscribe((data) => (this.data = data));
}

响应标题图像

Answer 1

您需要在后端设置 Access-Control-Expose-Headers 以公开您的自定义响应 header 。

取自 Mozilla Docs on Access-Control-Expose-Headers :

The Access-Control-Expose-Headers response header indicates which headers can be exposed as part of the response by listing their names.

By default, only the 6 CORS-safelisted response headers are exposed:

Cache-Control, Content-Language, Content-Type, Expires, Last-Modified, Pragma

If you want clients to be able to access other headers, you have to list them using the Access-Control-Expose-Headers header.

因此，您必须对后端进行编码以设置Access-Control-Expose-Headers，以便它返回:

Access-Control-Expose-Headers:x-total-count、x-next-page、x-per-page

或者

访问控制公开 header :*

这是一个简单的 stackblitz为了供您探索，您可以在 StackBlitz 的控制台中观察到我可以检索 Etag header ，但不能 X-Frame-Options 因为 https://api.github.com已设置 Access-Contorl-Expose-Headers 来公开 Etag，但不公开 X-Frame-Options: