How redirect to another server with post nodejs?

Nodejs, express. I have form like this:

<form action="https://anothersite.com/post" method="POST">
      <input type="hidden" name="field1" value="val1">
      <input type="hidden" name="field2" value="val2">
      <button type="submit">Send</button>
</form>

I need this one:

<form action="/mypost" method="POST">
      <button type="submit">Send</button>
</form>

..that means I send empty post to page /mypost on my server and question: how to redirect to another server in backend with sending post data?