如何获取Angular 2响应头

Question

I am using Angular 2 to request JSON from my Rails API server. My server is set to respond with a header X-Total-Count: 10 . My server is successfully sending those headers:

But when I try to console.log(res.headers) the http response, I only receive a _headersMap with Content-Type and Cache-Control :

Here is my Rack::Cors config:

config.middleware.insert_before 0, "Rack::Cors" do
    allow do
        origins '*'
        resource '*', headers: :any, methods: [:get, :post, :options, :patch, :delete], expose: ['X-Total-Count']
    end
end

And the way I'm setting the headers in the controller:

  def index
    ...
    @posts = ...

    response.headers['X-Total-Count'] = '10'
    response.headers['Access-Control-Allow-Headers'] = 'X-Total-Count'

    render json: @posts
  end

How can I ensure that the X-Total-Count is appears in the _headersMap ? Or, how can I access the X-Total-Count value response?

Answer 1

Found the issue. Even though I was exposing the header through the Rack::Cors configuration, it didn't work until I made changes to fix this deprecation . Now, the following configuration, set in config/initializers/cors.rb , properly exposes the headers:

Rails.application.config.middleware.insert_before 0, Rack::Cors do
  allow do
    origins '*'
    resource '*',
    headers: :any,
    methods: [:get, :post, :put, :patch, :delete, :options, :head],
    expose: ['X-Total-Count']
  end
end

Answer 2

According to this bug posted in alpha this is caused by your browser considering certain headers "unsafe" and rejecting their access. The fix in that thread was to add a header to your server response:

access-control-expose-headers: x-total-count

Answer 3

It's because of CORS. You're only be able to see the header in the map only if it's enabled by CORS.

Your server needs to return the following in headers:

Access-Control-Allow-Headers: X-Total-Count