For image find attr "title" and replace with "alt"

For image find attr "title" and replace with "alt"

I am trying to replace the "title"(not assigned) of each image with the assigned alternative text.

For example:

Before:
<img src="imagesYolloSwag.jpg" alt="swag" width="136" height="143" > // title not defined


After:
<img src="imagesYolloSwag.jpg" alt="swag" width="136" height="143" > 

// title added, and value picked from alt text

What am i doing wrong here? Please help.

<script>
$(document).ready(function() {
$('img').each(function() {
                   var altX = $(this).attr('alt');
$(this).attr('title').replaceWith(altX);
        });
        
    });
</script>