Using get_template_part() for Componentized WordPress Themes

button.php

<?php
/**
 * $args is available with all values passed in third parameter of get_template_part()
 *
 * In a real theme, this would go in something like parts/button.php or components/button.php
 *
 * Think carefully about which $args you assume will always be available and which you need to check for
 *
 * @link https://developer.wordpress.org/reference/functions/get_template_part/
 */
<a class="my-super-sweet-button <?php echo esc_attr( $args['extra_classes'] ?? '' ); ?>"
   href="<?php echo esc_url( $args['href'] ); ?>">
	<?php echo esc_html( $args['label'] ); ?>
</a>

index.php

/**
 * Any WordPress Template
 */
<!-- header stuff -->
<?php
get_template_part('parts/button', '', array(
	  'label' => 'Click me!',
	  'href' => 'https://example.com',
	  'extra_classes' => 'custom-class',
) );
?>
<!-- footer stuff -->