Add polyfills for IE11

js/_frontend.js

@@ -52,6 +52,27 @@ const wpdtrtAnchorlinksUi = {
         return $(`.wpdtrt-anchorlinks__list-link[href='#${$(el).attr('id')}']`);
     },
 
+    /**
+     * @function initPolyfills
+     * @memberof wpdtrtAnchorlinksUi
+     * @protected
+     */
+    initPolyfill: () => {
+        /* eslint-disable */
+
+        // Polyfill for forEach
+        if (window.NodeList && !NodeList.prototype.forEach) {
+            NodeList.prototype.forEach = Array.prototype.forEach;
+        }
+
+        // Polyfill for forEach
+        if (window.HTMLCollection && !HTMLCollection.prototype.forEach) {
+            HTMLCollection.prototype.forEach = Array.prototype.forEach;
+        }
+
+        /* eslint-enable */
+    },
+
     /**
      * @function setTitleToSummary
      * @summary Inject the summary section (outside of the page content) into the nav.
@@ -272,6 +293,8 @@ const wpdtrtAnchorlinksUi = {
     sticky_jump_menu: ($jumpMenu) => {
         const $ = wpdtrtAnchorlinksUi.jQuery;
 
+        wpdtrtAnchorlinksUi.initPolyfill();
+
         if (!$jumpMenu.length) {
             return;
         }