diff --git a/layout/_partials/head/head-unique.njk b/layout/_partials/head/head-unique.njk
index 7aa8308..5424909 100644
--- a/layout/_partials/head/head-unique.njk
+++ b/layout/_partials/head/head-unique.njk
@@ -1,6 +1,11 @@
 {{ open_graph() }}
 
-{{ canonical() }}
+{# https://github.com/theme-next/hexo-theme-next/issues/866 #}
+{%- set canonical = url | replace(r/index\.html$/, '') %}
+{%- if not config.permalink.endsWith('.html') %}
+  {%- set canonical = canonical | replace(r/\.html$/, '') %}
+{%- endif %}
+<link rel="canonical" href="{{ canonical }}">
 
 {# Exports some front-matter variables to Front-End #}
 <script{{ pjax }} class="page-configurations">
diff --git a/layout/_partials/page/breadcrumb.njk b/layout/_partials/page/breadcrumb.njk
index 267617f..4405b65 100644
--- a/layout/_partials/page/breadcrumb.njk
+++ b/layout/_partials/page/breadcrumb.njk
@@ -1,13 +1,11 @@
 {%- set paths = page.path.split('/') %}
 {%- set count = paths.length %}
 {%- if count > 2 %}
-  {%- set current = 0 %}
   {%- set link = '' %}
   <ul class="breadcrumb">
     {%- for path in paths %}
-      {%- set current = current + 1 %}
       {%- if path != 'index.html' %}
-        {%- if current == count - 1 and paths[count - 1] == 'index.html' %}
+        {%- if loop.index == count - 1 and paths[loop.index] == 'index.html' %}
           <li>{{ path | upper }}</li>
         {% else %}
           {%- if link == '' %}
@@ -15,8 +13,8 @@
           {% else %}
             {%- set link = link + '/' + path %}
           {%- endif %}
-          {%- if path.includes('.html') %}
-            <li>{{ path | replace('.html', '') | upper }}</li>
+          {%- if path.endsWith('.html') %}
+            <li>{{ path | replace(r/\.html$/, '') | upper }}</li>
           {% else %}
             <li><a href="{{ url_for(link) }}/">{{ path | upper }}</a></li>
           {%- endif %}
diff --git a/layout/_third-party/quicklink.njk b/layout/_third-party/quicklink.njk
index b94fc65..fc49376 100644
--- a/layout/_third-party/quicklink.njk
+++ b/layout/_third-party/quicklink.njk
@@ -7,7 +7,7 @@
       quicklink.listen({
         timeout : {{ page.quicklink.timeout }},
         priority: {{ page.quicklink.priority }},
-        ignores : [uri => uri.includes('#'),uri => uri === '{{ url | replace('index.html', '') }}',{{ page.quicklink.ignores }}]
+        ignores : [uri => uri.includes('#'),uri => uri === '{{ url | replace(r/index\.html$/, '') }}',{{ page.quicklink.ignores }}]
       });
     {%- if page.quicklink.delay %}
       });
diff --git a/scripts/events/lib/vendors.js b/scripts/events/lib/vendors.js
index bb58627..f87256d 100644
--- a/scripts/events/lib/vendors.js
+++ b/scripts/events/lib/vendors.js
@@ -32,6 +32,6 @@ module.exports = hexo => {
     let { plugins = 'jsdelivr' } = vendors;
     if (plugins === 'cdnjs' && unavailable && unavailable.includes('cdnjs')) plugins = 'jsdelivr';
     if (plugins === 'local' && typeof internal === 'undefined') plugins = 'jsdelivr';
-    vendors[key] = links[plugins];
+    vendors[key] = links[plugins] || links.jsdelivr;
   }
 };
diff --git a/scripts/helpers/engine.js b/scripts/helpers/engine.js
index 069d92b..5ad64d7 100644
--- a/scripts/helpers/engine.js
+++ b/scripts/helpers/engine.js
@@ -15,16 +15,15 @@ hexo.extend.helper.register('next_inject', function(point) {
     .join('');
 });
 
-hexo.extend.helper.register('next_js', function(url, pjax = false) {
+hexo.extend.helper.register('next_js', function(file, pjax = false) {
   const { next_version } = this;
-  const { js } = this.theme;
   const { internal } = this.theme.vendors;
-  let src = this.url_for(`${js}/${url}`);
-  if (internal === 'jsdelivr') {
-    src = `//cdn.jsdelivr.net/npm/hexo-theme-next@${next_version}/source/js/${url}`;
-  } else if (internal === 'unpkg') {
-    src = `//unpkg.com/hexo-theme-next@${next_version}/source/js/${url}`;
-  }
+  const links = {
+    local   : this.url_for(`${this.theme.js}/${file}`),
+    jsdelivr: `//cdn.jsdelivr.net/npm/hexo-theme-next@${next_version}/source/js/${file}`,
+    unpkg   : `//unpkg.com/hexo-theme-next@${next_version}/source/js/${file}`
+  };
+  const src = links[internal] || links.local;
   return `<script ${pjax ? 'data-pjax ' : ''}src="${src}"></script>`;
 });
 
@@ -59,20 +58,9 @@ hexo.extend.helper.register('post_nav', function(post) {
 
 hexo.extend.helper.register('gitalk_md5', function(path) {
   const str = this.url_for(path);
-  str.replace('index.html', '');
   return crypto.createHash('md5').update(str).digest('hex');
 });
 
-hexo.extend.helper.register('canonical', function() {
-  // https://support.google.com/webmasters/answer/139066
-  const { permalink } = hexo.config;
-  let url = this.url.replace(/index\.html$/, '');
-  if (!permalink.endsWith('.html')) {
-    url = url.replace(/\.html$/, '');
-  }
-  return `<link rel="canonical" href="${url}">`;
-});
-
 /**
  * Get page path given a certain language tag
  */