How can we pass form parameters to a url in post request.?

function sendUsingPost(url,formFields){ 
    var urlP = url;
    var params = formFields.replace(",", "&");
    http.open("POST", urlP, true);
    
    //Send the proper header information along with the request
    http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    http.setRequestHeader("Content-length", params.length);
    http.setRequestHeader("Connection", "close");
    
    http.onreadystatechange = function() {//Call a function when the state changes.
      if(http.readyState == 4 && http.status == 200) {
		alert(http.responseText);
      }
    }
      http.send(params);
  }