JSFiddle - React, Tailwind, and code Playground

HTML

<a href="#" id="download" data-params="{'ca_id':'12'}"><button name="download"></button></a>

JavaScript

$(document).ready(function(){
    
    $("#download").click(function(){
        var me = $(this); 
        data = me.data('params');
        alert($.type(data)+'---------'+data);
        saveData(data); // was me
});
    
    function saveData(data){
        
        $.ajax({
           type: "POST",
           url: "download_counter.php",
           data: { client_id: "<? echo $client_id;?>", candidate_id: me }
        });
    }
});