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<!-- START code - disable button after form submission -->
<script type="text/javascript">
    window.instapageFormSubmitSuccess = function(form) {
       var element = window.__page_generator ? document.querySelectorAll('.widget .btn.form-btn.item-block') : document.querySelectorAll('.widget-form .btn.submit-button.button_submit.dynamic-button');
        for (var i = 0; i < element.length; i++) {
            element[i].disabled = true;
        }
    };
 </script>
<!-- END code - disable button after form submission -->

<!-- START code - disable button after form submission -->
<script type="text/javascript">
    window.instapageFormSubmitSuccess = function(form) {
       var element = document.querySelectorAll('.widget .btn.form-btn.item-block');
        for (var i = 0; i < element.length; i++) {
            element[i].disabled = true;
        }
    };
 </script>
<!-- END code - disable button after form submission -->