MemberPress: Auto-populate coupon on all registration forms

function mepr_auto_populate_coupon() { 

?>

  <script>

  (function($) {

    $(document).ready(function() {

      var c = $('.mepr_coupon input.mepr-coupon-code');

      if(c) {

        // Paste coupon below to replace 'YOURCOUPON'

        c.val('YOURCOUPON');

      }

    });

  })(jQuery)

  </script>

<?php 

}

add_action( 'wp_head', 'mepr_auto_populate_coupon' );