使用Ajax在WordPress中插入数据

In WordPress, I'm trying to insert data into database using Ajax.

functions.php

function dataInsert(){
    global $wpdb, $slidecount;
    $slidecount = 25;
    $wpdb->insert(
        'custom_table',
        array(
            'slidecount'=> $slidecount
        )
    );
    die();
    return true;
}
add_action('wp_ajax_dataInsert', 'dataInsert');
add_action('wp_ajax_nopriv_dataInsert', 'dataInsert');

JavaScript// I put insertDataJS function in footer.php

<script>
function insertDataJS(){
   console.log("insertDataJS start");
   jQuery.ajax({
      type: 'POST',
      url: dataInsert.ajaxurl,
      data: {"action": "dataInsert"},
      success: function(data){
           //alert(data);
      }
   });
   console.log("insertDataJS end");
}
</script>

When I tried to call the insertDataJS() function, I get the error messages below:

Uncaught ReferenceError: dataInsert is not defined at insertDataJS ((index):303) at HTMLDivElement. ((index):444) at HTMLDivElement.dispatch (jquery.js?ver=1.12.4:3) at HTMLDivElement.r.handle (jquery.js?ver=1.12.4:3) at Object.trigger (jquery.js?ver=1.12.4:3) at n.fn.init.triggerHandler (jquery.js?ver=1.12.4:3) at Object.changeTo (eval at (layerslider.kreaturamedia.jquery.js?ver=6.7.6:13), :1:53999) at Object.eval (eval at (layerslider.kreaturamedia.jquery.js?ver=6.7.6:13), :1:131795) at Object.g._callback (greensock.js?ver=1.19.0:20) at Object.g.render (greensock.js?ver=1.19.0:21)

Please share any idea!

As @Inazo and @Outsource suggested in their answer, I sloved it by using the ajaxurl javascript variable to reference the admin-ajax.php file. I declared this on the front end, by putting the following in the footer.php of my theme.

<script type="text/javascript">
    var ajaxurl = "<?php echo admin_url('admin-ajax.php'); ?>";
</script>