async-fetch-sql

// Fetches SQL table through ajax POST
// console.logs rows as JSON

// =============================== PHP (functions.php)
<?php

add_action( 'wp_ajax_clients', 'sql_get_clients' );
add_action( 'wp_ajax_nopriv_clients', 'sql_get_clients' ); // postman (if user not logged in)

function sql_get_clients() {

  global $wpdb;

  $query  = "SELECT * FROM table_name";
  $result = $wpdb -> get_results($query);

  echo json_encode($result);

  die();
}

?>

// =============================== JS
async function sql_getclients() {
  try{
    var url = ajaxurl; // 

    var data = new URLSearchParams();
    data.append('action', 'clients');

    var req = await fetch(url, {
      method: 'POST',
      headers: { "Content-Type": "application/x-www-form-urlencoded" },
      body: data
    });

    var val      = await req.text();
    var val_json = JSON.parse(val);

    console.log(val_json);
  }catch(e){
    console.log(e);
  }
}