Watch for changes to dark mode (#34)

Author: kculmback

prefers-dark.js

@@ -2,8 +2,19 @@ function checkDarkMode() {
   return window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches;
 }
 
-if (checkDarkMode()) {
-  document.documentElement.classList.add('mode-dark');
-} else {
-  document.documentElement.classList.remove('mode-dark');
+function watchDarkMode() {
+  if (!window.matchMedia) return;
+
+  window.matchMedia('(prefers-color-scheme: dark)').addListener(addDarkModeSelector);
+}
+
+function addDarkModeSelector() {
+  if (checkDarkMode()) {
+    document.documentElement.classList.add('mode-dark');
+  } else {
+    document.documentElement.classList.remove('mode-dark');
+  }
 }
+
+addDarkModeSelector();
+watchDarkMode();