// const root = document.documentElement; // , not
// const btn = document.getElementById("toggleTheme");
//
// const savedTheme = localStorage.getItem("theme") || "light";
// root.className = savedTheme;
// btn.innerHTML = savedTheme === "dark" ? "✧" : "☾";
//
// btn.addEventListener("click", () => {
// const newTheme = root.classList.contains("light") ? "dark" : "light";
// root.className = newTheme;
// localStorage.setItem("theme", newTheme);
// btn.innerHTML = newTheme === "dark" ? "✧" : "☾";
// });
/**
* Utility function to calculate the current theme setting.
* Look for a local storage value.
* Fall back to system setting.
* Fall back to light mode.
*/
function calculateSettingAsThemeString({ localStorageTheme, systemSettingDark }) {
if (localStorageTheme !== null) {
return localStorageTheme;
}
if (systemSettingDark.matches) {
return "dark";
}
return "light";
}
/**
* Utility function to update the button text and aria-label.
*/
function updateButton({ buttonEl, isDark }) {
const newCta = isDark ? "Change to light theme" : "Change to dark theme";
const newInnerText = isDark ? "✧" : "☾";
// use an aria-label if you are omitting text on the button
// and using a sun/moon icon, for example
buttonEl.setAttribute("aria-label", newCta);
buttonEl.innerText = newInnerText;
}
/**
* Utility function to update the theme setting on the html tag
*/
function updateThemeOnHtmlEl({ theme }) {
document.querySelector("html").setAttribute("data-theme", theme);
}
/**
* On page load:
*/
/**
* 1. Grab what we need from the DOM and system settings on page load
*/
const button = document.querySelector("[data-theme-toggle]");
const localStorageTheme = localStorage.getItem("theme");
const systemSettingDark = window.matchMedia("(prefers-color-scheme: dark)");
/**
* 2. Work out the current site settings
*/
let currentThemeSetting = calculateSettingAsThemeString({ localStorageTheme, systemSettingDark });
/**
* 3. Update the theme setting and button text accoridng to current settings
*/
updateButton({ buttonEl: button, isDark: currentThemeSetting === "dark" });
updateThemeOnHtmlEl({ theme: currentThemeSetting });
/**
* 4. Add an event listener to toggle the theme
*/
button.addEventListener("click", (event) => {
const newTheme = currentThemeSetting === "dark" ? "light" : "dark";
localStorage.setItem("theme", newTheme);
updateButton({ buttonEl: button, isDark: newTheme === "dark" });
updateThemeOnHtmlEl({ theme: newTheme });
currentThemeSetting = newTheme;
});