diff --git a/layouts/partials/footer.html b/layouts/partials/footer.html
index 2070942bb3..4fe3947846 100644
--- a/layouts/partials/footer.html
+++ b/layouts/partials/footer.html
@@ -42,7 +42,7 @@
       {{- $.Scratch.Set "mermaidInitialize" "{ \"startOnLoad\": true }" }}
   {{- end }}
     <script>
-      if (mermaid) {
+      if (typeof mermaid != 'undefined') {
         mermaid.mermaidAPI.initialize( Object.assign( { "securityLevel": "antiscript" }, JSON.parse({{ $.Scratch.Get "mermaidInitialize" }}), { startOnLoad: false } ) );
       }
     </script>
diff --git a/static/js/relearn.js b/static/js/relearn.js
index 840a8ef5ff..cbf867d0df 100644
--- a/static/js/relearn.js
+++ b/static/js/relearn.js
@@ -104,7 +104,7 @@ function initMermaid() {
         $(element).parent().replaceWith('<div class="mermaid" align="center">' + content + '</div>');
     });
 
-    if (mermaid) {
+    if (typeof mermaid != 'undefined') {
         mermaid.mermaidAPI.initialize( Object.assign( {}, mermaid.mermaidAPI.getSiteConfig(), { startOnLoad: true } ) );
         mermaid.contentLoaded();
         $(".mermaid svg").svgPanZoom({})
@@ -538,7 +538,7 @@ jQuery(function() {
 
 jQuery.extend({
     highlight: function(node, re, nodeName, className) {
-        if (node.nodeType === 3 && node.parentElement.namespaceURI == 'http://www.w3.org/1999/xhtml') { // text nodes
+        if (node.nodeType === 3 && node.parentElement && node.parentElement.namespaceURI == 'http://www.w3.org/1999/xhtml') { // text nodes
             var match = node.data.match(re);
             if (match) {
                 var highlight = document.createElement(nodeName || 'span');
diff --git a/static/js/search.js b/static/js/search.js
index 82c906ec43..8065cf1bfb 100644
--- a/static/js/search.js
+++ b/static/js/search.js
@@ -45,7 +45,7 @@ function initLunr() {
 function search(term) {
     // Find the item in our index corresponding to the lunr one to have more info
     // Remove Lunr special search characters: https://lunrjs.com/guides/searching.html
-    var searchTerm = lunr.tokenizer(term.replace(/[*:^~+-]/, ' ')).flatMap(token => searchPatterns(token.str)).join(' ');
+    var searchTerm = lunr.tokenizer(term.replace(/[*:^~+-]/, ' ')).reduce( function(a,token){return a.concat(searchPatterns(token.str))}, []).join(' ');
     return !searchTerm ? [] : lunrIndex.search(searchTerm).map(function(result) {
         return { index: result.ref, matches: Object.keys(result.matchData.metadata) }
     });
@@ -75,7 +75,7 @@ $(function() {
             var page = pagesIndex[item.index];
             var numContextWords = 2;
             var contextPattern = '(?:\\S+ +){0,' + numContextWords + '}\\S*\\b(?:' +
-                item.matches.map(match => match.replace(/\W/g, '\\$&')).join('|') +
+                item.matches.map( function(match){return match.replace(/\W/g, '\\$&')} ).join('|') +
                 ')\\b\\S*(?: +\\S+){0,' + numContextWords + '}';
             var context = page.content.match(new RegExp(contextPattern, 'i'));
             var divcontext = document.createElement('div');