Using find() and first() and replaceWith() with XML document

Question

I am reading in an XML document and would like to find the first tag of a specific name, and replace that instance with a different tag and contents. I am using find and first, but the replaceWith call is not replacing it.

$(storyXML).find('oldTag').first().replaceWith('<newTag>text</newTag>') ;
  });

The find is finding multiple oldTags, the first is returning the first of them, the replaceWith is doing nothing. After searching around Stack Overflow, I even tried replacing all of them using:

$(storyXML).find('oldTag').each(function() {
    $(this).replaceWith('<newTag>text</newTag>') ;
  });

But that didn't do anything either. I appreciate any help you can offer!

EDIT: storyXML is being assigned here (tried to simplify the code for posting, hopefully it still makes sense):

var load = function () {
    var fn;

    fn = function (obj, init) {
        storyXML = obj.responseXML;
    };

    ajax("GET", this.url, null, fn);
};

---

EDIT 2: Fixed code via Jason's answer below. Posting for anyone else having this issue and lost finding a workaround like I was.

  var xmlDoc = $.parseXML( storyXML );
  var $xml = $( xmlDoc );
  $xml.find('oldTag').first().replaceWith('<newTag>stuff</newTag>');

  // if you want to keep the old XML string updated, need to do this step
  storyXML = (new XMLSerializer()).serializeToString(xmlDoc);

Answer 1

Have you tried https://api.jquery.com/jQuery.parseXML/ ? Sometimes jQuery will operate on either strings or DOM objects, but other times jQuery expects objects.