luci-theme-privaterouter/luasrc/app.js

(function () {
  // your page initialization code here
  // the DOM will be available here

  const toggler = document.querySelector(".toggler");
  console.log(toggler);
  toggler.addEventListener(
    "click",
    function (e) {
      const element = document.querySelector(".navbar");
      element.classList.toggle("active");
    },
    false
  );

  const isDark = localStorage.getItem("isDark");
  if (isDark == 1) {
    const element = document.querySelector("body");
    element.classList.add("dark");
  }
  const themetoggler = document.querySelector(".themetoggler");
  themetoggler.addEventListener(
    "click",
    function (e) {
      e.preventDefault();
      const element = document.querySelector("body");
      element.classList.toggle("dark");

      const isDark = localStorage.getItem("isDark");
      localStorage.setItem("isDark", isDark == 1 ? 0 : 1);
    },
    false
  );

  document.addEventListener("DOMContentLoaded", function() {
    // Move all your code here
  
    var mutationObserver = new MutationObserver(function(mutations) {
      mutations.forEach(function(mutation) {
        var checkboxes = document.querySelectorAll('.cbi-checkbox input[type="checkbox"]');
    
        checkboxes.forEach(function(checkbox) {
          // Check if toggle switch is already created
          if (!checkbox.nextSibling || checkbox.nextSibling.className !== 'switch') {
            var switchElement = document.createElement('label');
            switchElement.className = 'switch';
          
            var input = document.createElement('input');
            input.type = 'checkbox';
            input.checked = checkbox.checked;
            switchElement.appendChild(input);
          
            var slider = document.createElement('span');
            slider.className = 'slider';
            switchElement.appendChild(slider);
          
            // Add the switch to the div wrapping the checkbox
            checkbox.parentNode.insertBefore(switchElement, checkbox);
          
            // Hide the original checkbox
            checkbox.style.display = 'none';
          
            input.addEventListener('change', function() {
                checkbox.checked = this.checked;
            });
          
            var observer = new MutationObserver(function() {
                input.checked = checkbox.checked;
            });
            observer.observe(checkbox, { attributes: true });
          }
        });
      });
    });
    
    mutationObserver.observe(document.documentElement, { childList: true, subtree: true });
  });

})(); // Make sure to include this closing partz