Quick way to add a custom tracking script to the WooCommerce thank you / order confirmation page and prevent it from running multiple times in the event of a user page refresh.

WC: Add Confirmation Tracking Scripts (Run Once).php

<?php // Don't Include

// Run Scripts on Order Confirmation Endpoint in WooCommerce Once.
function zf_woocommerce_thankyou_scripts($order_id) {
	// Check for meta key on order, only run if not found.
	if( ! get_post_meta( $order_id , '_tracking_scripts_ran', true ) ) {
		// Add meta key to order so scripts don't run a second time.
		add_post_meta( $order_id, '_tracking_scripts_ran', 'yes', true );  ?>
		
		<script type="text/javascript">
			<!-- Your Tracking Script(s) here --> 
		</script>
	
	<?php }
}
add_action( 'woocommerce_thankyou', 'zf_woocommerce_thankyou_scripts' );