使用 javascript 切换按钮上的文本

Question

I'm trying to create a dark mode toggle button and I require following text properties :-

1. Turn on dark mode should appear when theme is a light one
2. Turn off dark mode should appear if theme is dark one.

Nothing more, Currently, I'm using follwing code to toggle between dark and light mode but the issue comes with button. I tried different codes but the text gets swapped in a wrong manner. https://codepen.io/vkdatta27/pen/oNxrxad .

<script>const btn = document.querySelector(".btn-toggle");

const currentTheme = localStorage.getItem("theme");
if (currentTheme == "dark") {
  document.body.classList.add("dark"); 
}

btn.addEventListener("click", function () {
  document.body.classList.toggle("dark");

  let theme = "light";
  if (document.body.classList.contains("dark")) {
    theme = "dark"; 
 
  }

  localStorage.setItem("theme", theme);
});
</script>
<style>
.btn-toggle {
border-radius: 20px;
float: center;
outline: none;
border: 25px;
padding: 10px;
width: fit;
font-size: 15px;
cursor: pointer;
-webkit-tap-highlight-color: transparent;
text-align:center;
box-shadow:  5px 5px 10px #5c5c5f, 
             -5px -5px 10px #ffffff;
background-color: #101010;
color: #e6e7ee;
}
body.dark .btn-toggle {
box-shadow:  5px 5px 10px #121212, 
             -5px -5px 10px #4a4a4a;
color: #101010 !important;
background-color: #e6e7ee;
}
body.dark .btn-toggle a {
color: #101010 !important;
}
body {background-color: #e6e7ee}
body.dark {background-color: #101010; color:#ffffff}
</style>
<button class="btn-toggle" id="btn-id"></button>

Answer 1

In your case you don't really need Javascript to get things done:

Logic:

• when .dark is off, show text 1 - this is the default
• when .dark is on, show text 2 - when CSS class .dark is active

CSS:

/* ADDED */
.btn-toggle::before { content: 'dark mode' }       /* default text of the button */
.dark .btn-toggle::before { content: 'light mode' }/* overwrite the default text*/
/*********/