我自己问题的解决方案：

将您的自定义file.js 并本地化admin-ajax.php.

index.php

    function script_enqueue() {

        // Register the JS file with a unique handle, file location, and an array of dependencies
        wp_register_script("dt_csc", plugin_dir_url(__FILE__).
            \'js/cdt.js\', array(\'jquery\'));

        // localize the script to your domain name, so that you can reference the url to admin-ajax.php file easily
        wp_localize_script(\'dt_csc\', \'myAjax\', array(\'ajaxurl\' => admin_url(\'admin-ajax.php\')));

        // enqueue jQuery library and the script you registered above
        wp_enqueue_script(\'jquery\');
        wp_enqueue_script(\'dt_csc\');
    }
    add_action(\'init\', \'script_enqueue\');

index.php

if ( !function_exists( \'client_json\' ) ) {

    function client_json() {
        //global object to perform database operation
        global $wpdb;
        //include the php file responsible for generating json for datatable 
        include_once plugin_dir_path( __FILE__ ) . \'/datatables/client.php\';
        // Kills WordPress execution  
        wp_die();
    }
    // wp_ajax is a authenticated Ajax
    add_action(\'wp_ajax_client_json\', \'client_json\' ); 
    //wp_ajax_nopriv is a non-authenticated Ajax
    add_action(\'wp_ajax_nopriv_client_json\', \'client_json\' ); 
}

cdt.js

var client_table = jQuery(\'#client_table\').DataTable({
       "lengthChange": false,
       "autoWidth": false,
       "searching": true,
       "ordering": false,
       "processing":true,
       "serverSide":true,
       "order":[],
       "ajax":{
         url:"admin-ajax.php",
         data:{action:"client_json"},
         type:"POST"
       },
       "columnDefs":[
         {
           "targets":[0],
           "orderable":false,
         },
       ],
});