diff --git a/_includes/js-selector.html b/_includes/js-selector.html
new file mode 100644
index 0000000..f8f40c7
--- /dev/null
+++ b/_includes/js-selector.html
@@ -0,0 +1,164 @@
+<!-- JS selector for site. -->
+
+<!-- commons -->
+
+{% assign urls = site.data.origin[type].jquery.js
+  | append: ','
+  | append: site.data.origin[type].bootstrap.js
+  | append: ','
+  | append: site.data.origin[type].search.js
+%}
+
+<!-- layout specified -->
+
+{% if page.layout == 'post' or page.layout == 'page' or page.layout == 'home' %}
+  {% assign urls = urls | append: ',' | append: site.data.origin[type]['lazy-polyfill'].js %}
+
+  {% unless page.layout == 'home' %}
+    <!-- image lazy-loading & popup & clipboard -->
+    {% assign urls = urls
+      | append: ','
+      | append: site.data.origin[type]['magnific-popup'].js
+      | append: ','
+      | append: site.data.origin[type].clipboard.js
+    %}
+  {% endunless %}
+{% endif %}
+
+{% if page.layout == 'home'
+  or page.layout == 'post'
+  or page.layout == 'archives'
+  or page.layout == 'category'
+  or page.layout == 'tag'
+%}
+  {% assign locale = site.lang | split: '-' | first %}
+
+  {% assign urls = urls
+    | append: ','
+    | append: site.data.origin[type].dayjs.js.common
+    | append: ','
+    | append: site.data.origin[type].dayjs.js.locale
+    | replace: ':LOCALE', locale
+    | append: ','
+    | append: site.data.origin[type].dayjs.js.relativeTime
+    | append: ','
+    | append: site.data.origin[type].dayjs.js.localizedFormat
+  %}
+{% endif %}
+
+{% if page.content contains '<h2' or page.content contains '<h3' and site.toc and page.toc %}
+  {% assign urls = urls | append: ',' | append: site.data.origin[type].toc.js %}
+{% endif %}
+
+{% if page.mermaid %}
+  {% assign urls = urls | append: ',' | append: site.data.origin[type].mermaid.js %}
+{% endif %}
+
+{% include jsdelivr-combine.html urls=urls %}
+
+{% case page.layout %}
+  {% when 'home', 'categories', 'post', 'page' %}
+    {% assign js = page.layout %}
+  {% when 'archives', 'category', 'tag' %}
+    {% assign js = 'misc' %}
+  {% else %}
+    {% assign js = 'commons' %}
+{% endcase %}
+
+{% capture script %}/assets/js/dist/{{ js }}.min.js{% endcapture %}
+<script defer src="{{ script | relative_url }}"></script>
+
+{% if page.math %}
+  <!-- MathJax -->
+  <script>
+    /* see: <https://docs.mathjax.org/en/latest/options/input/tex.html#tex-options> */
+    MathJax = {
+      tex: {
+        /* start/end delimiter pairs for in-line math */
+        inlineMath: [
+          ['$', '$'],
+          ["\\(", "\\)"]
+        ],
+        /* start/end delimiter pairs for display math */
+        displayMath: [
+          ['$$', '$$'],
+          ["\\[", "\\]"]
+        ],
+        macros: {
+          ds: "\\displaystyle",
+
+          // font styles
+          rm: ["\\mathrm{#1}", 1],
+          mf: ["\\mathfrak{#1}", 1],
+          mc: ["\\mathcal{#1}", 1],
+          bb: ["\\mathbb{#1}", 1],
+          bf: ["\\mathbf{#1}", 1],
+          tt: ["\\texttt{#1}", 1],
+
+          inv: "^{-1}",
+          conj: "^\\ast",
+          trans: "^\\top",
+          cross: "^\\times",
+          bs: "\\setminus",
+          nsub: "\\unlhd",
+          pnsub: "\\lhd",
+
+          floor: ["\\left\\lfloor #1 \\right\\rfloor", 1],
+          ceil: ["\\left\\lceil #1 \\right\\rceil", 1],
+          round: ["\\left\\lfloor #1 \\right\\rceil", 1],
+          norm: ["\\left\\lVert #1 \\right\\rVert", 1],
+          abs: ["\\left\\lvert #1 \\right\\rvert", 1],
+          paren: ["\\left( #1 \\right)", 1],
+          braces: ["\\left\\{ #1 \\right\\}", 1],
+          span: ["\\left\\langle #1 \\right\\rangle", 1],
+          bar: ["\\overline{#1 \\vphantom{l}}", 1],
+
+          lcm: ["\\mathrm{lcm}"],
+
+          ra: "\\rightarrow",
+          la: "\\leftarrow",
+          lra: "\\leftrightarrow",
+          imp: "\\implies",
+          pll: "\\parallel",
+
+          N: "\\mathbb{N}",
+          Z: "\\mathbb{Z}",
+          Q: "\\mathbb{Q}",
+          R: "\\mathbb{R}",
+          C: "\\mathbb{C}",
+          F: "\\mathbb{F}",
+
+          Adv: ["\\mathrm{Adv}_{\\mathrm{#1}}[#2]", 2, ""],
+
+          im: "\\operatorname\{im\}",
+          ch: "\\operatorname\{char\}",
+
+          Aut: "\\mathrm{Aut}",
+          Gal: "\\mathrm{Gal}",
+          GF: "\\mathrm{GF}",
+
+          exists: "∃\\,",
+
+          tilde: ["\\widetilde{#1}", 1],
+          hat: ["\\widehat{#1}", 1],
+        }
+      }
+    };
+  </script>
+  <script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script>
+  <script id="MathJax-script" async src="{{ site.data.origin[type].mathjax.js | relative_url }}"></script>
+{% endif %}
+
+{% if jekyll.environment == 'production' %}
+  <!-- PWA -->
+  {% if site.pwa.enabled %}
+    <script defer src="{{ '/app.js' | relative_url }}"></script>
+  {% else %}
+    <script defer src="{{ '/unregister.js' | relative_url }}"></script>
+  {% endif %}
+
+  <!-- GA -->
+  {% if site.google_analytics.id != empty and site.google_analytics.id %}
+    {% include google-analytics.html %}
+  {% endif %}
+{% endif %}