toggle button not functioning

I’m creating a to-do list app for my portfolio and I’d like to add a dark-mode feature for my body/background. however, my toggle button looks fine but the switch doesn’t seem to function and I can’t seem to figure out why anyone sees anything wrong or that may be interfering?

function dark() { // setting up dark-mode 
  var element = document.body;
  element.classList.toggle("dark-mode"); //dark-mode class
label {
  margin: 10px;
  cursor: pointer;
  width: 50px;
  height: 30px;
  display: block;
  border-radius: 50px;
  position: relative;
  color: white;

.switch {
  position: relative;
  display: inline-block;
  width: 110px;
  height: 10px;
  margin: 0 10px;

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: aqua;
  transition: .4s;
  border-radius: 35px;

.switch input {
  display: none

.slider::before {
  position: absolute;
  content: "";
  height: 20px;
  width: 20px;
  left: 5px;
  bottom: 5px;
  background-color: white;
  transition: 0.4s;
  border-radius: 50px;

input:checked+.slider {
  background-color: blue;

input:checked+.slider::before {
  transform: translateX(0px);

input:checked+.slider::after {
  transform: translateX(8px);
<div class="toggle">
  <label for="switch">
        <input type="checkbox" onclick="dark()" checked>
        <span class="slider"></span>