add darkmode switch

js/main.js

@@ -27,3 +27,29 @@ function timeago() {
     });
   });
 })();
+
+var darkSwitch = document.getElementById("darkSwitch");
+window.addEventListener("load", function () {
+  if (darkSwitch) {
+    initTheme();
+    darkSwitch.addEventListener("change", function () {
+      resetTheme();
+    });
+  }
+});
+
+function initTheme() {
+  var darkThemeSelected = localStorage.getItem("darkSwitch") !== null && localStorage.getItem("darkSwitch") === "dark";
+  darkSwitch.checked = darkThemeSelected;
+  darkThemeSelected ? document.body.setAttribute("data-theme", "dark") : document.body.removeAttribute("data-theme");
+}
+
+function resetTheme() {
+  if (darkSwitch.checked) {
+    document.body.setAttribute("data-theme", "dark");
+    localStorage.setItem("darkSwitch", "dark");
+  } else {
+    document.body.removeAttribute("data-theme");
+    localStorage.removeItem("darkSwitch");
+  }
+}