Checkout Block Order Note field customization

add_action( 'woocommerce_blocks_enqueue_checkout_block_scripts_after', function() {

	?>
	<script type="text/javascript">
	document.addEventListener( 'DOMContentLoaded', function() {

		// Await Checkout Block Order Note Load
		let checkoutBlockInterval = setInterval( function() {

			let orderNoteWrap = '.wc-block-checkout__add-note';

			// Not Loaded Yet
			if( document.querySelector( orderNoteWrap ) === null ) {
				return;
			}

			// Loaded
			clearInterval( checkoutBlockInterval );

			document.querySelectorAll( orderNoteWrap )
				.forEach( function( wrap ) {

				// Adjust Label Text
				wrap.querySelector( '.wc-block-components-checkbox__label' )
					.innerHTML = 'Custom title for the order notes field';

				// Create Custom Field
				wrap.querySelector( '.wc-block-components-checkbox__input' )
					.addEventListener( 'change', function( checkbox ) {
					if( checkbox.target.checked ) {
						wrap.querySelector( '.wc-block-components-textarea' )
							.placeholder = 'Custom placeholder here';
					}
				} );

			} );

		}, 500 ); // End Await Checkout Block Order Note Load

	} );
	</script>
	<?php

} );