Replace html tag in a string using AngularJS

I have a string containing html tags :

var str =  "<div><p></p><p><i>blabla</i></p><p><i><b>blaaaaaablaaaaa</b></i></p><iframe src='urlAAA' height='400' width='800'></iframe><p></p><p><sub>hello blabla</sub></p><p><br></p><iframe src='urlBBB' height='400' width='800'></iframe></div>"; 

I want to replace each <iframe> tag with <button> tag in this way:

"<button type="button">Click Me for iframe n°1 !</button>" for first iframe

"<button type="button">Click Me for iframe n°2 !</button>" for second iframe

etc....

I'm using angularJS. I think the solution is to do something like this :

var ele = angular.element(str);
ele.replaceWith(function(index){
        return "<button type='button'>Click Me for iframe n°" + index + " !</button>";
});

But I don't know how to specify this for <iframe> tags

Any suggestion ? Thanks !

---

EDIT :

Here a new example, what I want to do :

In var str I have 2 <iframe> tags with different src attribute value :

the first iframe has src='urlAAA' the second src='urlBBB'

I want to get access to the src attribute and replace it with an another url.

function editFrameAttributes(str){
      var array =[];
      var eles= angular.element(str).find('iframe');
      [].forEach.call(eles, function (ctl) {
        array.push(ctl.outerHTML)
      });
      Object.keys(array).forEach(function (key) {
        var tempEl = document.createElement('div');
        tempEl.innerHTML = array[key];

        tempEl.childNodes[0].attributes['src'].value = "www.something.com";
        tempEl.childNodes[0].attributes['width'].value = '1234';

        array[key] = tempEl.innerHTML;
      });
      //then I don't know how to replace old iframes by new iframes in 'str' 

      return newStr;
    }

The output should look like this :

var str =  "<div><p></p><p><i>blabla</i></p><p><i><b>blaaaaaablaaaaa</b></i></p><div><iframe src='www.something.com' height='400' width='1234'></iframe></div><p></p><p><sub>hello blabla</sub></p><p><br></p><div><iframe src='www.something.com' height='400' width='1234'></iframe></div></div>";