Parsley Validation – Adds overlay once the form is successfully submitted to stop user from selecting submit multiple times.

parsley-form.scss

.parsley, .webform-client-form .form-item .parsley {
    &-success {
        outline: 1px solid $green;
    }
    &-error {
        outline: 1px solid red;
    }
    &-errors-list {
        display: none;
    }
}

.form-disabled {
    position: relative;
    &::before {
        left: 0;
        top: 0;
        bottom: 0;
        right: 0;
        content: " ";
        position: absolute;
        width: 100%;
        height: 100%;
        background: white;
        opacity: 0.8;
        z-index: 11;
        display: block;
    }
    &::after {
        content: " ";
        width: 40px;
        height: 40px;
        position: absolute;
        display: block;
        z-index: 12;
        margin: -40px 0 0 -20px;
        top: 50%;
        left: 50%;
        background-color: #333;
        border-radius: 100%;
        -webkit-animation: sk-scaleout 1.0s infinite ease-in-out;
        animation: sk-scaleout 1.0s infinite ease-in-out;
    }

    @-webkit-keyframes sk-scaleout {
      0% { -webkit-transform: scale(0) }
      100% {
        -webkit-transform: scale(1.0);
        opacity: 0;
      }
    }

    @keyframes sk-scaleout {
      0% {
        -webkit-transform: scale(0);
        transform: scale(0);
      } 100% {
        -webkit-transform: scale(1.0);
        transform: scale(1.0);
        opacity: 0;
      }
    }

}

parsley-init.js

/* global subscribe */
(function(app, $, window, document, undefined) {
	'use strict';

	// Add class "no-validate" to exclude form from being validated.
	var $webForm = $('.webform-client-form').not('.no-validate');

    // Test for form on page
    if ( $webForm.length ){
        // Init Parsley Validation
        $webForm.parsley();

        // On Parsley Form Success, Add Class of 'form-disabled' to form
        window.Parsley.on('form:success', function() {
            $webForm.addClass('form-disabled');
        });
    }

})(window.app = window.app || {}, $, window, document);

Example: