Load JavaScript once on the page if a core block exists. As adapted from https://wordpress.stackexchange.com/a/328553

my-plugin.php

function enqueue_my_awesome_script_if_there_is_block( $content = '' ) {
	if ( has_block( 'core/list' ) ) {
		wp_enqueue_script(
			'my-awesome-script',
			plugins_url( 'hello-world.js', __FILE__ ),
			array(),
			'0.1.1',
			true
		);
	}

	return $content;
}
add_filter( 'the_content', 'enqueue_my_awesome_script_if_there_is_block' );