use custom price displayed from js in woocommerce code example

Example: include in the price html woocommerce

add_filter( 'woocommerce_get_price_html', 'wpa83367_price_html', 100, 2 );
function wpa83367_price_html( $price, $product ){
    return 'Was:' . str_replace( '', ' Now:', $price );
}