This is an animated custom HTML element which toggles between light theme, dark theme, and automatic theme (OS theme). It adds a custom attribute (data-theme) to the html element of your page. You can style your page the way you like based on the value of that attribute.

See the demo page and scroll below for an example.

• Regular HTML pages

  <script src="https://unpkg.com/@mahozad/theme-switch"></script>

• Node.js and npm

  npm install --save @mahozad/theme-switch

  <script src="node_modules/@mahozad/theme-switch/dist/theme-switch.min.js"></script>

• Angular and more

  For Angular framework and more details about each of the above installation methods see the wiki.

After installing the library, use the element like this (make sure to include the end tag):

<theme-switch></theme-switch>

A custom element is no different from the built-in elements of HTML.
Use and style it however you want just like you would use and style a regular element (e.g. a div):

theme-switch {
  width: 64px;
  padding: 8px;
  background: #888;
  
  /* There is a special property called --theme-switch-icon-color
   * which you can set, to change the color of the icon in the switch */
  --theme-switch-icon-color: #aabbcc;
}

In your CSS stylesheet, specify your desired styles for light and dark themes. One way is to define custom CSS properties for your colors, sizes, etc. and redefine them (if needed) with new values for the other theme:

/* These are applied for the default (light) theme */
/* (or when the toggle is auto, and the OS theme is light) */
html {
  --my-page-background-color: #fff;
  --my-icons-color: #000;
  --my-primary-color: red;
}

/* These are applied for the dark theme */
/* (or when the toggle is auto, and the OS theme is dark) */
/* If a property has the same value for both light and dark themes, no need to redeclare it here */
html[data-theme="dark"] {
  --my-page-background-color: #112233;
  --my-icons-color: #efefef;
}

body {
  background: var(--my-page-background-color);
}

document.addEventListener("themeToggle", event => {
  console.log(`Old theme: ${ event.detail.oldState }`);
  console.log(`New theme: ${ event.detail.newState }`);
  // More operations...
});