How do I access query parameters in the request content body in javascript?

If I use a GET to request a page, then I can access any query parameters from javascript using window.location.search. Is there a similar way to access query parameters which are in the request content body rather than the request location, when the page is a result of a POST?

From stackoverflow

• Because the data is being handled on the server side, the client (where JS lives) has no access to these variables.