Hide the default "Add to cart" button and show a customized "Add to cart" button in WooCommerce

functions.php

<?php
/*
 * 
 * Customized add to cart button for WooCommerce
 * © mahdyar.me (hasanpour@mahdyar.me)
 * 
 * Add this to the end of your template's "functions.php" file (without "<?php" at the begining of this file)
 * 
 */

// to hide the default add to cart button
add_filter( 'woocommerce_is_purchasable', '__return_false');

// to show a customized add to cart button
add_action( 'woocommerce_single_product_summary', 'custom_button_after_product_summary', 30 );
function custom_button_after_product_summary() {
  echo "<!-- Custom add-to-cart button! -->";
}