diff --git a/layout/_partials/comments.njk b/layout/_partials/comments.njk
index 961789f..030b383 100644
--- a/layout/_partials/comments.njk
+++ b/layout/_partials/comments.njk
@@ -16,9 +16,9 @@
       {%- endfor %}
       <script{{ pjax }}>
         (function() {
-          let commentButton = document.querySelectorAll('.comment-button');
+          const commentButton = document.querySelectorAll('.comment-button');
             commentButton.forEach(element => {
-            let commentClass = element.classList[2];
+            const commentClass = element.classList[2];
             element.addEventListener('click', () => {
               commentButton.forEach(active => active.classList.toggle('active', active === element));
               document.querySelectorAll('.comment-position').forEach(active => active.classList.toggle('active', active.classList.contains(commentClass)));
@@ -32,7 +32,7 @@
             activeClass = localStorage.getItem('comments_active') || activeClass;
           }
           if (activeClass) {
-            let activeButton = document.querySelector(`.comment-button.${activeClass}`);
+            const activeButton = document.querySelector(`.comment-button.${activeClass}`);
             if (activeButton) {
               activeButton.click();
             }
@@ -65,7 +65,7 @@
       activeClass = localStorage.getItem('comments_active') || activeClass;
     }
     if (activeClass) {
-      let activeTab = document.querySelector(`a[href="#comment-${activeClass}"]`);
+      const activeTab = document.querySelector(`a[href="#comment-${activeClass}"]`);
       if (activeTab) {
         activeTab.click();
       }
@@ -74,7 +74,7 @@
   if (CONFIG.comments.storage) {
     window.addEventListener('tabs:click', event => {
       if (!event.target.matches('.tabs-comment .tab-content .tab-pane')) return;
-      let commentClass = event.target.classList[1];
+      const commentClass = event.target.classList[1];
       localStorage.setItem('comments_active', commentClass);
     });
   }
diff --git a/layout/_third-party/math/mathjax.njk b/layout/_third-party/math/mathjax.njk
index e834198..24a7eea 100644
--- a/layout/_third-party/math/mathjax.njk
+++ b/layout/_third-party/math/mathjax.njk
@@ -26,7 +26,7 @@
           }, '', false],
           insertedScript: [200, () => {
             document.querySelectorAll('mjx-container').forEach(node => {
-              let target = node.parentNode;
+              const target = node.parentNode;
               if (target.nodeName.toLowerCase() === 'li') {
                 target.parentNode.classList.add('has-jax');
               }
diff --git a/layout/_third-party/statistics/lean-analytics.njk b/layout/_third-party/statistics/lean-analytics.njk
index 2b82251..647e90f 100644
--- a/layout/_third-party/statistics/lean-analytics.njk
+++ b/layout/_third-party/statistics/lean-analytics.njk
@@ -52,7 +52,7 @@
         .then(response => response.json())
         .then(({ results }) => {
           for (let url of entries) {
-            let target = results.find(item => item.url === url);
+            const target = results.find(item => item.url === url);
             leancloudSelector(url).innerText = target ? target.time : 0;
           }
         })
@@ -61,7 +61,7 @@
         });
     }
 
-    let { app_id, app_key, server_url } = {{ theme.leancloud_visitors | safedump }};
+    const { app_id, app_key, server_url } = {{ theme.leancloud_visitors | safedump }};
     function fetchData(api_server) {
       const Counter = (method, url, data) => {
         return fetch(`${api_server}/1.1${url}`, {
diff --git a/layout/_third-party/tags/pdf.njk b/layout/_third-party/tags/pdf.njk
index a781105..30cafcd 100644
--- a/layout/_third-party/tags/pdf.njk
+++ b/layout/_third-party/tags/pdf.njk
@@ -2,16 +2,16 @@
 {%- set pdf_uri = url_for('lib/pdf/web/viewer.html') %}
 <script{{ pjax }}>
 document.querySelectorAll('.pdfobject-container').forEach(element => {
-  let url = element.dataset.target;
-  let pdfOpenParams = {
+  const url = element.dataset.target;
+  const pdfOpenParams = {
     navpanes : 0,
     toolbar  : 0,
     statusbar: 0,
     pagemode : 'thumbs',
     view     : 'FitH'
   };
-  let pdfOpenFragment = '#' + Object.entries(pdfOpenParams).map(([key, value]) => `${key}=${encodeURIComponent(value)}`).join('&');
-  let fullURL = `{{ pdf_uri }}?file=${encodeURIComponent(url)}${pdfOpenFragment}`;
+  const pdfOpenFragment = '#' + Object.entries(pdfOpenParams).map(([key, value]) => `${key}=${encodeURIComponent(value)}`).join('&');
+  const fullURL = `{{ pdf_uri }}?file=${encodeURIComponent(url)}${pdfOpenFragment}`;
 
   if (NexT.utils.supportsPDFs()) {
     element.innerHTML = `<embed class="pdfobject" src="${url + pdfOpenFragment}" type="application/pdf" style="height: ${element.dataset.height};">`;
diff --git a/source/js/schedule.js b/source/js/schedule.js
index dc7c548..42f3021 100644
--- a/source/js/schedule.js
+++ b/source/js/schedule.js
@@ -33,7 +33,8 @@
     maxResults  : calendar.maxResults
   };
 
-  const request_url = 'https://www.googleapis.com/calendar/v3/calendars/' + calendar.calendar_id + '/events?' + Object.entries(params).map(([key, value]) => `${key}=${encodeURIComponent(value)}`).join('&');
+  const request_url = new URL(`https://www.googleapis.com/calendar/v3/calendars/${calendar.calendar_id}/events`);
+  Object.entries(params).forEach(param => request_url.searchParams.append(...param));
 
   function getRelativeTime(current, previous) {
     const msPerMinute = 60 * 1000;
@@ -96,7 +97,7 @@
     const eventList = document.querySelector('.event-list');
     if (!eventList) return;
 
-    fetch(request_url).then(response => {
+    fetch(request_url.href).then(response => {
       return response.json();
     }).then(data => {
       if (data.items.length === 0) {