watch system theme

watchSystemTheme.js

const watchSystemTheme = (cb) => { // I will use callback for that
  // Addlistener to matchmedia for light and dark mode
  window.matchMedia("(prefers-color-scheme: dark)").addListener(e => {
    e.matches && cb("dark"); // If it is dark we called the defined callback with dark argument
  })
  window.matchMedia("(prefers-color-scheme: light)").addListener(e => {
    e.matches && cb("light"); // Else If it is dark we called the defined callback with light argument
  })
}