How Do I Use Objective-C (ObjC) with JavaScript for Automation (JXA) to create HTTP request?

Question

I created a simple http request in the following way:

source: Getting HTML Source from a URL without a Web Browser

var urlStr = "https://stackoverflow.com/";
var htmlStr = getHTMLSource(urlStr);
htmlStr.substring(0,200);

function getHTMLSource(pURL) {
  var nsURL     = $.NSURL.URLWithString(pURL);
  var nsHTML    = $.NSData.dataWithContentsOfURL(nsURL);
  var nsHTMLStr = $.NSString.alloc.initWithDataEncoding(nsHTML, $.NSUTF8StringEncoding);

  var htmlStr   = ObjC.unwrap(nsHTMLStr);

  return htmlStr;
}

However, how do I create a POST request and set the request header？