picocss/docs/js/src/theme-switcher.js

/*
 * Theme switcher
 *
 * Pico.css - https://picocss.com
 * Copyright 2019-2021 - Licensed under MIT
 */

export const themeSwitcher = {

  // Config
  _scheme: 'auto',
  change: {
    light: '<i>Turn on dark mode</i>',
    dark: '<i>Turn off dark mode</i>'
  },
  buttonsTarget: '.theme-switcher',



  // Init
  init() {
    this.scheme = this._scheme;
    this.initSwitchers();
  },


  // Prefered color scheme
  get preferedColorScheme() {
    if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
      return 'dark';
    }
    else {
      return 'light';
    }
  },


  // Init switchers
  initSwitchers() {
    const buttons = document.querySelectorAll(this.buttonsTarget);
    buttons.forEach(function(button) {
      button.addEventListener('click', function(event) {
        if (this.scheme == 'dark') {
          this.scheme = 'light';
        }
        else {
          this.scheme = 'dark';
        }
      }.bind(this), false);
    }.bind(this));
  },


  // Add new button
  addButton(config) {

    // Insert Switcher
    let button = document.createElement(config.tag);
    button.className = config.class;
    document.querySelector(config.target).appendChild(button);
  },


  // Set scheme
  set scheme(scheme) {

    if (scheme == 'auto') {
      if (this.preferedColorScheme == 'dark') {
        this._scheme = 'dark';
      }
      else {
        this._scheme = 'light';
      }
    }

    // Set to Dark
    else if (scheme == 'dark' || scheme == 'light') {
      this._scheme = scheme;
    }

    // Set to Apply theme
    this.applyScheme();
  },


  // Get scheme
  get scheme() {
    return this._scheme;
  },


  // Apply scheme
  applyScheme() {

    // Root attribute
    document.querySelector('html').setAttribute('data-theme', this.scheme);

    // Buttons text
    const buttons = document.querySelectorAll(this.buttonsTarget);
    let text;
    buttons.forEach(function(button) {
      if (this.scheme == 'dark') {
        text = this.change.dark;
      }
      else {
        text = this.change.light;
      }
      button.innerHTML = text;
      button.setAttribute('aria-label', text.replace(/<[^>]*>?/gm, ''));
    }.bind(this));
  }
}

export default themeSwitcher;