Change WooCommerce Add To Cart test on product page

gistfile1.php

<?php

// The Add to cart form is in this template file
// /woocommerce/templates/single-product/add-to-cart/simple.php
// and calls WC_Product::single_add_to_cart_text() to get the text for the button.
// This is the filter that is set around that text.
add_filter('woocommerce_product_single_add_to_cart_text', 'growdev_change_addtocart');
function growdev_change_addtocart( $arg ) {
  // Change the argument to the new text for the button
	$arg = "BUY NOW";
	return $arg;

}