Resolve #2493183 "8.x 3.x ajax support 273"

Closes #2493183

js/recaptcha.js

+/**
+ * @file
+ * Contains the definition of the behaviour recaptcha.
+ */
+
+(function ($, Drupal) {
+  Drupal.behaviors.recaptcha = {
+    attach: function (context) {
+      $('.g-recaptcha', context).each(function () {
+        if (typeof grecaptcha === 'undefined' || typeof grecaptcha.render !== 'function') {
+          return;
+        }
+        if ($(this).closest('body').length > 0) {
+          if ($(this).hasClass('recaptcha-processed')) {
+            grecaptcha.reset();
+          }
+          else {
+            grecaptcha.render(this, $(this).data());
+            $(this).addClass('recaptcha-processed');
+          }
+        }
+      });
+    }
+  };
+
+  window.drupalRecaptchaOnload = function () {
+    $('.g-recaptcha').each(function () {
+      if (!$(this).hasClass('recaptcha-processed')) {
+        grecaptcha.render(this, $(this).data());
+        $(this).addClass('recaptcha-processed');
+      }
+    });
+  };
+})(jQuery, Drupal);