Get URL from ahref using Javascript

<a href="#url" data-mc-cta="1" style="display:none">Link</a>

In this above a href code, a random URL will be generated by advertising network javascript placed before </head> tag

I am trying to get the random URL value using JS code :

var maxConvLink = document.querySelector('a[data-mc-cta="1"]');
var mcLink = maxConvLink.getAttribute("href");
alert(mcLink);	

This code is placed before </body> tag. The problem is this above JS code getting value #url instead of real random URL value.

As far i know, Javascript work in sequence, so, first Ad network JS code will place url to a href tag and than my code will get the value but it not working as I think.

There are different approaches to achieve the output. Choose the one that best suits your needs.

Using Window.onload

window.onload = function() {
  var maxConvLink = document.querySelector('a[data-mc-cta="1"]');
  var mcLink = maxConvLink.getAttribute("href");
  alert(mcLink);	
}

Using jQuery document ready function

$(document).ready(function() {
  var maxConvLink = document.querySelector('a[data-mc-cta="1"]');
  var mcLink = maxConvLink.getAttribute("href");
  alert(mcLink);    
});

in order to use the jQuery library, you will need to include it

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>

Using DOMContentLoaded event

document.addEventListener("DOMContentLoaded", function() {
  var maxConvLink = document.querySelector('a[data-mc-cta="1"]');
  var mcLink = maxConvLink.getAttribute("href");
  alert(mcLink);
});

Using setTimeout:

setTimeout(function() {
  var maxConvLink = document.querySelector('a[data-mc-cta="1"]');
  var mcLink = maxConvLink.getAttribute("href");
  alert(mcLink);
}, 1000);

Using setInterval:

var intervalId = setInterval(function() {
  var maxConvLink = document.querySelector('a[data-mc-cta="1"]');
  if (maxConvLink) {
    clearInterval(intervalId);
    var mcLink = maxConvLink.getAttribute("href");
    alert(mcLink);
  }
}, 1000);

Using MutationObserver

var targetNode = document.querySelector('a[data-mc-cta="1"]');

var observer = new MutationObserver(function(mutations) {
  mutations.forEach(function(mutation) {
    if (mutation.type === "attributes" && mutation.attributeName === "href") {
      var maxConvLink = mutation.target;
      var mcLink = maxConvLink.getAttribute("href");
      alert(mcLink);
    }
  });
});

observer.observe(targetNode, {
  attributes: true
});

Using IntersectionObserver

var targetNode = document.querySelector('a[data-mc-cta="1"]');

var observer = new IntersectionObserver(function(mutations) {
  mutations.forEach(function(mutation) {
    if (mutation.type === "attributes" && mutation.attributeName === "href") {
      var maxConvLink = mutation.target;
      var mcLink = maxConvLink.getAttribute("href");
      alert(mcLink);
    }
  });
});

observer.observe(targetNode, {
  attributes: true
});

Using window.addEventListener

window.addEventListener("load", function() {
  var maxConvLink = document.querySelector('a[data-mc-cta="1"]');
  var mcLink = maxConvLink.getAttribute("href");
  alert(mcLink);	
});