website-risg/templates/app.js

document.addEventListener('DOMContentLoaded', function() {
  changeTheme();
  initcolorTheme();
  apply_stickies()
});

function changeTheme() {
  let toggleBtn = document.querySelector('#theme-toggle-js');

  if(toggleBtn) {
    toggleBtn.addEventListener('click', function() {
      if(toggleBtn.dataset.theme === 'light') {
        setTheme('dark', true);
      } else {
        setTheme('light', true);
      }
    });
  } 
}

/***
* init javascript
* 1) detect native color scheme or use set theme in local storage
* 2) detect view (desktop or responsive) if on mobile device with touch screen
* 3) set base font size to 112.5% -> 18px
*/
function initcolorTheme() {
  colorThemeWatcher();
  let theme = localStorage.getItem('theme');
  if (theme == null || theme === 'auto') {
      if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) {
          setTheme('dark', false);
      } else {
          setTheme('light', false);
      }
  } else {
      setTheme(theme)
  }
}

/***
* Listener operating system native color configuration
*/
function colorThemeWatcher() {
  try {
      window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', e => {
          setTheme(e.matches ? 'dark' : 'light');
      });
  } catch {
      console.warn('color theme watcher not supported');
  }
}

/**
* Define color scheme, colors without losing the base font size configuration
* and add data-theme to html tag
* @param theme
*/
function setTheme(theme, setLocalStorage = true) {
  let toggleBtn = document.querySelector('#theme-toggle-js');

  if (setLocalStorage) {
    localStorage.setItem('theme', theme);
  }
  if (toggleBtn) toggleBtn.setAttribute('data-theme', theme);

  if (document.documentElement.dataset.theme === 'dark' && theme === 'light') {
      document.documentElement.dataset.theme = 'light';
  } else if(document.documentElement.dataset.theme === 'light' && theme === 'dark'){
      document.documentElement.dataset.theme = 'dark';
  }
}

window.addEventListener('scroll', function() {
    apply_stickies()
})

function apply_stickies() {
    var _$stickies = [].slice.call(document.querySelectorAll('.sticky'))
    _$stickies.forEach(function(_$sticky) {
        if (CSS.supports && CSS.supports('position', 'sticky')) {
            apply_sticky_class(_$sticky)
        }
    })
}

function apply_sticky_class(_$sticky) {
    var currentOffset = _$sticky.getBoundingClientRect().top
    var stickyOffset = parseInt(getComputedStyle(_$sticky).top.replace('px', ''))
    var isStuck = currentOffset <= stickyOffset

    _$sticky.classList.toggle('js-is-sticky', isStuck)
}