Hybrid WooCommerce Product Category Widget (Dropdown PLUS Subcategory List)

functions.php

<?php

/**
 * Adds customized product categories widget with subcategories (when applicable).
 */
class subcat_widget extends WP_Widget {

	/**
	 * Register widget with WordPress.
	 */
	function __construct() {
		parent::__construct(
			'subcat_widget', // Base ID
			esc_html__( 'Custom Categories Widget', 'text_domain' ), // Name
			array( 'description' => esc_html__( 'Display categories and sub-categories', 'text_domain' ), ) // Args
		);
	}

	/**
	 * Front-end display of widget.
	 *
	 * @see WP_Widget::widget()
	 *
	 * @param array $args     Widget arguments.
	 * @param array $instance Saved values from database.
	 */
	public function widget( $args, $instance ) {
		echo $args['before_widget'];
		
		if ( ! empty( $instance['title'] ) ) {
			echo $args['before_title'] . apply_filters( 'widget_title', $instance['title'] ) . $args['after_title'];
		}
		
		wc_product_dropdown_categories( array( 'show_count' => 0 , 'hide_empty' => 1 ) );
		
		$parentid = get_queried_object_id();
         
		$args = array(
			'parent' => $parentid
		);
		 
		$terms = get_terms( 'product_cat', $args );
		 
		if ( $terms ) {
				 
			echo '<ul class="product-categories store-links">';
			 
				foreach ( $terms as $term ) {
								 
					echo '<li class="cat-item">';                 
						echo '<a href="' .  esc_url( get_term_link( $term ) ) . '" class="' . $term->slug . '">';
							echo $term->name;
						echo '</a>';
					echo '</li>';
				}
				
			echo '</ul>';
		}
		
		echo '</div>';
		
		?>
		<script type='text/javascript'>
		/* <![CDATA[ */
			var product_cat_dropdown = jQuery(".dropdown_product_cat");
			product_cat_dropdown.change(function() {
				if ( product_cat_dropdown.val() !=='' ) {
					location.href = "<?php echo home_url(); ?>/?product_cat="+product_cat_dropdown.val();
				}
			});
		/* ]]> */
		</script>
		<?php
		
		echo $args['after_widget'];
	}

	/**
	 * Back-end widget form.
	 *
	 * @see WP_Widget::form()
	 *
	 * @param array $instance Previously saved values from database.
	 */
	public function form( $instance ) {
		$title = ! empty( $instance['title'] ) ? $instance['title'] : esc_html__( 'Product Categories', 'text_domain' );
		?>
		<p>
		<label for="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>"><?php esc_attr_e( 'Title:', 'text_domain' ); ?></label> 
		<input class="widefat" id="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'title' ) ); ?>" type="text" value="<?php echo esc_attr( $title ); ?>">
		</p>
		<?php 
	}

	/**
	 * Sanitize widget form values as they are saved.
	 *
	 * @see WP_Widget::update()
	 *
	 * @param array $new_instance Values just sent to be saved.
	 * @param array $old_instance Previously saved values from database.
	 *
	 * @return array Updated safe values to be saved.
	 */
	public function update( $new_instance, $old_instance ) {
		$instance = array();
		$instance['title'] = ( ! empty( $new_instance['title'] ) ) ? strip_tags( $new_instance['title'] ) : '';

		return $instance;
	}

} // class subcat_widget

// register subcat_widget widget
function register_subcat_widget() {
    register_widget( 'subcat_widget' );
}
add_action( 'widgets_init', 'register_subcat_widget' );