Javascript Update href of <a> tag on page load

Question

I've written a code that looks like this. I should update every href of the tags that have the url I want to change.

<script>
   var url = window.location.href;
   myArr = url.split("?");
   myArr[0] = "mynewurl";
   new_url = myArr.join("#");

   $(document).ready(function(){

          $(".item a[href='myoldurl']").prop("href", new_url);

   });
   </script>

Unfortunately the href is always the same. Here is the button in which my tag is contained.

<div class="de elBTN elAlign_center elMargin0 ui-droppable de-editable" id="tmp_button-57701" data-de-type="button" data-de-editing="false" data-title="button" data-ce="false" data-trigger="none" data-animate="fade" data-delay="500" style="margin-top: 30px; outline: none; cursor: pointer;" data-element-theme="customized" data-elbuttontype="1" aria-disabled="false">
<a href="https://pietroscataglini.typeform.com/to/c4dAZYjg" class="elButton elButtonSize1 elButtonColor1 elButtonRounded elButtonPadding2 elButtonFluid elButtonBlock elButtonCorner5 elBTNone elBtnVP_10 elBtnHP_20 elBTN_b_none elButtonShadow3 elButtonTxtColor1 deneg1pxLetterSpacing ea-buttonPulseGlow mfs_20" style="color: rgb(255, 255, 255); background: rgb(55, 149, 128); font-size: 20px;" rel="noopener noreferrer">
<span class="elButtonMain"><i class="fa_prepended fas fa-angle-double-right" contenteditable="false"></i>“Voglio diventare un Copywriter!"<i class="fa_appended fas fa-angle-double-left" contenteditable="false"></i></span>
<span class="elButtonSub mfs_14" style="font-size: 18px;">Compila il questionario per accedere alla consulenza gratuita introduttiva</span>
</a>
</div>

Here is the tag:

<a href="myoldurl" class="elButton elButtonSize1 elButtonColor1 elButtonRounded elButtonPadding2 elButtonFluid elButtonBlock elButtonCorner5 elBTNone elBtnVP_10 elBtnHP_20 elBTN_b_none elButtonShadow3 elButtonTxtColor1 deneg1pxLetterSpacing ea-buttonPulseGlow mfs_20" style="color: rgb(255, 255, 255); background: rgb(55, 149, 128); font-size: 20px;" rel="noopener noreferrer">
<span class="elButtonMain"><i class="fa_prepended fas fa-angle-double-right" contenteditable="false"></i>“Voglio diventare un Copywriter!"<i class="fa_appended fas fa-angle-double-left" contenteditable="false"></i></span>
<span class="elButtonSub mfs_14" style="font-size: 18px;">Compila il questionario per accedere alla consulenza gratuita introduttiva</span>
</a>
     

Answer 1

You don't need to .item class name in query selector because your <a> element hasn't this class. Try this.

btn.onclick = function changeUrl () {
  var newUrl = "https://pietroscataglini.typeform.com/to/c4dAZYjg";
  /*
  var myArr = url.split("?");
  myArr[0] = "mynewurl";
  var new_url = myArr.join("#");
  */

  $("a[href='myoldurl']").prop("href", newUrl);
  $("#message").text(newUrl);
}

#message {
 color: red
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div class="de elBTN elAlign_center elMargin0 ui-droppable de-editable" id="tmp_button-57701" data-de-type="button" data-de-editing="false" data-title="button" data-ce="false" data-trigger="none" data-animate="fade" data-delay="500" style="margin-top: 30px; outline: none; cursor: pointer;" data-element-theme="customized" data-elbuttontype="1" aria-disabled="false">
  <a href="myoldurl" class="elButton elButtonSize1 elButtonColor1 elButtonRounded elButtonPadding2 elButtonFluid elButtonBlock elButtonCorner5 elBTNone elBtnVP_10 elBtnHP_20 elBTN_b_none elButtonShadow3 elButtonTxtColor1 deneg1pxLetterSpacing ea-buttonPulseGlow mfs_20" style="color: rgb(255, 255, 255); background: rgb(55, 149, 128); font-size: 20px;" rel="noopener noreferrer">
    <span class="elButtonMain"><i class="fa_prepended fas fa-angle-double-right" contenteditable="false"></i>“Voglio diventare un Copywriter!"<i class="fa_appended fas fa-angle-double-left" contenteditable="false"></i></span>
    <span class="elButtonSub mfs_14" style="font-size: 18px;">Compila il questionario per accedere alla consulenza gratuita introduttiva</span>
  </a>
</div>
<br>
Now <b>href</b> value is <span id="message">"myoldurl"</span>. 
<br>When you click on the button it will replace with your new url.
<br>
<input type="button" id="btn" value = "Change">

Answer 2

You can do like this

    let anc = document.getElementsByTagName('a');
    for (const ancr of anc) {
        if (ancr.href.includes('myoldurl')) {
            const ahref = ancr.href.replace('myoldurl', 'mynewurl');
            ancr.href = ahref;
        }
    }