bootstrap-js

// Register Script
function custom_scripts() {

	wp_register_script( 'bootstrap-js', 'https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js', false, '4.1.3', true );
	wp_enqueue_script( 'bootstrap-js' );

	wp_register_script( 'bootstrap-jq', 'https://code.jquery.com/jquery-3.3.1.slim.min.js', false, '3.3.1', true );
	wp_enqueue_script( 'bootstrap-jq' );

	wp_register_script( 'bootstrap-popper', 'https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js', false, '1.14.3', true );
	wp_enqueue_script( 'bootstrap-popper' );

}
add_action( 'wp_enqueue_scripts', 'custom_scripts' );