I am trying to set cookie to domain same as src of js file.

Scenario:
In www.xyz.com html, I have included js file from qwe.com as below

<script type=application/javascript src=http://qwe.com/b.js></script>

From this b.js, i want to create cookie with domain set to .qwe.com. I am setting cookie with following function

function createCookie(name, value, days) {

    if (days) {

      var date = new Date();

      date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));

      var expires = ; expires= + date.toGMTString();

    } else {

      var expires = ;

    }

    document.cookie = name+=+value+expires+;domain=.qwe.com+; path=/;;

  }

With above code I am unable to set cookie.
Example: www.flipkart.com-> Check cookies in resources tab of developer console-> .scorecardresearch.com and .doubleclick.net are able to set cookie

I want to do same. Can someone please share solution for this? Real working solution. I have tried multiple solutions by doing Google search. It didn't work.