I have this type of URL:
www.domain.com/postname?emailid=somethingsomething
I must place this part:
somethingsomething
inside WP header, more accurate inside JS snippet, as follows:
<script>
window.HashedEmail = 'somethingsomething';
</script>
EDIT: Suggested answer shows how to extract particular data but not how to place extracted data into header, for example - how to manipulate with extracted dataset
Maybe I missed something but this looks like a solution for me
const urlSearchParams = new URLSearchParams(window.location.search);
const emailid = urlSearchParams.get('emailid');
window.HashedEmail = emailid;