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jarv.is/assets/js/dark-mode.js

76 lines
2.4 KiB
JavaScript

/* jshint esversion: 6, indent: 2, browser: true, quotmark: single */
/*! Dark mode switcheroo | MIT License | jrvs.io/darkmode */
(function() {
// improve variable mangling when minifying
var win = window;
var doc = win.document;
var bod = doc.body;
var cls = bod.classList;
var sto = localStorage;
// check for preset `dark_mode_pref` preference in localStorage
var pref_key = 'dark_mode_pref';
var pref = sto.getItem(pref_key);
// change CSS via these <body> classes:
var dark = 'dark';
var light = 'light';
// use an element with class `dark-mode-toggle` to trigger swap when clicked
var toggle = doc.querySelector('.dark-mode-toggle');
// keep track of current state (light by default) no matter how we got there
var active = false;
// receives a class name and switches <body> to it
var activateTheme = function(theme) {
cls.remove(dark, light);
cls.add(theme);
active = (theme === dark);
};
// if user already explicitly toggled in the past, restore their preference
if (pref === dark) activateTheme(dark);
if (pref === light) activateTheme(light);
// user has never clicked the button, so go by their OS preference until/if they do so
if (!pref) {
// check for OS dark mode setting and switch accordingly
var prefers_dark = '(prefers-color-scheme: dark)';
var prefers_light = '(prefers-color-scheme: light)';
if (win.matchMedia(prefers_dark).matches)
activateTheme(dark);
else
activateTheme(light);
// real-time switching if supported by OS/browser
win.matchMedia(prefers_dark).addListener(function(e) { if (e.matches) activateTheme(dark); });
win.matchMedia(prefers_light).addListener(function(e) { if (e.matches) activateTheme(light); });
}
// don't freak out if page happens not to have a toggle
if (toggle) {
// toggle re-appears now that we know user has JS enabled
toggle.style.visibility = 'visible';
// handle toggle click
toggle.addEventListener('click', function() {
// switch to the opposite theme & save preference in local storage
if (!active) {
activateTheme(dark);
sto.setItem(pref_key, dark);
// send click event to analytics
sa_event('triggered_dark_mode');
} else {
activateTheme(light);
sto.setItem(pref_key, light);
// send click event to analytics
sa_event('triggered_light_mode');
}
}, true);
}
})();