plugin.php

<?php 
/*
Plugin Name: Ukazka vlozeni skriptu na thankyou page
*/

function lynt_ukazkova_akce( $order_id ) {
  ?>
  <script>
    console.log("thank you!");
  </script>
  <?php
}

add_action( "woocommerce_thankyou", "lynt_ukazkova_akce")