first commit

media/com_banners/js/admin-banner-edit.js

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+/**
+ * @copyright  (C) 2018 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license    GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+(document => {
+
+  const updateBannerFields = value => {
+    const imgWrapper = document.getElementById('image');
+    const custom = document.getElementById('custom');
+    switch (value) {
+      case '0':
+        // Image
+        imgWrapper.classList.remove('hidden');
+        custom.classList.add('hidden');
+        break;
+      case '1':
+        // Custom
+        imgWrapper.classList.add('hidden');
+        custom.classList.remove('hidden');
+        break;
+      // Do nothing
+    }
+  };
+
+  document.addEventListener('DOMContentLoaded', () => {
+    const jformType = document.getElementById('jform_type');
+    if (jformType) {
+      // Hide/show parameters initially
+      updateBannerFields(jformType.value);
+
+      // Hide/show parameters when the type has been selected
+      jformType.addEventListener('change', ({
+        target
+      }) => {
+        updateBannerFields(target.value);
+      });
+    }
+  });
+})(document);

media/com_banners/js/admin-banner-edit.min.js

@@ -0,0 +1 @@
+(e=>{const t=t=>{const d=e.getElementById("image"),s=e.getElementById("custom");switch(t){case"0":d.classList.remove("hidden"),s.classList.add("hidden");break;case"1":d.classList.add("hidden"),s.classList.remove("hidden")}};e.addEventListener("DOMContentLoaded",(()=>{const d=e.getElementById("jform_type");d&&(t(d.value),d.addEventListener("change",(({target:e})=>{t(e.value)})))}))})(document);