How to pass the value of each click to the anchor tag using jquery?

How to pass the value of each click to the anchor tag using jquery? I have this code here. I am trying to get the value every time I click the button

//My HTML
<button id="a-selectNm" data-a_name="<?php echo $row['username']; ?>"  data-toggle="modal" data-target="#selectNm">SELECT nursemaid</a>

//The modal
<div class="modal" id="selectNm">
<div class="card-body">
    <h4 class="card-title">
        <a href="#a_name"><?php echo $row['username']; ?></a>
    </h4>
</div>
</div>

//My jQuery code
jQuery(document).on('click', 'button#a-selectNm', function() {
    var a_name = jQuery(this).data('a_name');
    jQuery('.modal a[href="#a_name"]').val(a_name);
});
</script>

What's wrong with me, what do I need to change?