暗黑模式的初试2
我前面是试过暗黑模式吧，接下来就是实战。
大概是这样
首先是基本的html：
<main>
<article>
<h1>Dark mode should be a user preference—not presumed</h1>
<p>
Yes, by default, when a user has <code>@media (prefers-color-scheme: dark)</code> set, we should set a dark
theme, but we should also provide a
switch for if the dark them isn’t working out for them.
</p>
<p>This also benefits users that don’t have <code>@media (prefers-color-scheme: dark)</code> set because they
get a toggle to choose, too.</p>
</article>
<div class="user-toggle">
<div role="status" class="[ visually-hidden ][ js-mode-status ]"></div>
<button class="[ toggle-button ] [ js-mode-toggle ]">
<span class="[ toggle-button__text ] [ js-mode-toggle-text ]">Enable dark mode</span>
<span class="toggle-button__icon" aria-hidden="true"></span>
</button>
</div>
</main>
.user-toggle类就是我们的逻辑部分，接下来就是基本的css部分：
/* Presentational demo styles */
body {
font-family: sans-serif;
padding: 2rem 1rem;
line-height: 1.4;
display: grid;
place-items: center;
}
article {
max-width: 75ch;
margin: 0 auto;
}
article > * + * {
margin-top: 1em;
}
h1 {
font-size: 2.5rem;
line-height: 1.1;
}
p {
font-size: 1.2rem;
opacity: 0.9;
}
code {
font-weight: 700;
font-size: 1.3em;
white-space: pre;
}
.visually-hidden {
display: block;
height: 1px;
width: 1px;
overflow: hidden;
clip: rect(1px 1px 1px 1px);
clip: rect(1px, 1px, 1px, 1px);
clip-path: inset(1px);
white-space: nowrap;
position: absolute;
}
接下来对场景:root进行视觉定义，其中的<svg/>是按钮的图标，即太阳和月亮两个图标，在这里我们默认白昼模式为默认值，也就是css中的light部分：
:root {
--color-mode: 'light';
--color-dark: #141414;
--color-dark-alpha: rgba(0, 0, 0, 0.1);
--color-light: #efefef;
--color-light-alpha: rgba(255, 255, 255, 0.9);
--icon-sun: url('data:image/svg+xml,\
<svg version="1.1" xmlns="http://www.w3.org/2000/svg" fill="currentColor" viewBox="0 0 24 24">\
<path d="M18 12c0-0.811-0.161-1.587-0.455-2.295-0.304-0.735-0.75-1.395-1.303-1.948-0.552-0.552-1.213-0.998-1.948-1.303-0.707-0.293-1.483-0.454-2.294-0.454s-1.587 0.161-2.295 0.455c-0.735 0.304-1.395 0.75-1.948 1.302s-0.998 1.213-1.302 1.948c-0.294 0.708-0.455 1.484-0.455 2.295s0.161 1.587 0.455 2.295c0.304 0.735 0.75 1.395 1.303 1.948 0.552 0.552 1.213 0.998 1.948 1.303 0.707 0.293 1.483 0.454 2.294 0.454s1.587-0.161 2.295-0.455c0.735-0.304 1.395-0.75 1.948-1.303s0.998-1.213 1.303-1.948c0.293-0.707 0.454-1.483 0.454-2.294zM16 12c0 0.544-0.108 1.060-0.303 1.529-0.202 0.489-0.5 0.929-0.869 1.299s-0.81 0.667-1.299 0.869c-0.469 0.195-0.985 0.303-1.529 0.303s-1.060-0.108-1.529-0.303c-0.489-0.202-0.929-0.5-1.299-0.869s-0.667-0.81-0.869-1.299c-0.195-0.469-0.303-0.985-0.303-1.529s0.108-1.060 0.303-1.529c0.202-0.489 0.5-0.929 0.869-1.299s0.81-0.667 1.299-0.869c0.469-0.195 0.985-0.303 1.529-0.303s1.060 0.108 1.529 0.303c0.489 0.202 0.929 0.5 1.299 0.869s0.667 0.81 0.869 1.299c0.195 0.469 0.303 0.985 0.303 1.529zM11 1v2c0 0.552 0.448 1 1 1s1-0.448 1-1v-2c0-0.552-0.448-1-1-1s-1 0.448-1 1zM11 21v2c0 0.552 0.448 1 1 1s1-0.448 1-1v-2c0-0.552-0.448-1-1-1s-1 0.448-1 1zM3.513 4.927l1.42 1.42c0.391 0.391 1.024 0.391 1.414 0s0.391-1.024 0-1.414l-1.42-1.42c-0.391-0.391-1.024-0.391-1.414 0s-0.391 1.024 0 1.414zM17.653 19.067l1.42 1.42c0.391 0.391 1.024 0.391 1.414 0s0.391-1.024 0-1.414l-1.42-1.42c-0.391-0.391-1.024-0.391-1.414 0s-0.391 1.024 0 1.414zM1 13h2c0.552 0 1-0.448 1-1s-0.448-1-1-1h-2c-0.552 0-1 0.448-1 1s0.448 1 1 1zM21 13h2c0.552 0 1-0.448 1-1s-0.448-1-1-1h-2c-0.552 0-1 0.448-1 1s0.448 1 1 1zM4.927 20.487l1.42-1.42c0.391-0.391 0.391-1.024 0-1.414s-1.024-0.391-1.414 0l-1.42 1.42c-0.391 0.391-0.391 1.024 0 1.414s1.024 0.391 1.414 0zM19.067 6.347l1.42-1.42c0.391-0.391 0.391-1.024 0-1.414s-1.024-0.391-1.414 0l-1.42 1.42c-0.391 0.391-0.391 1.024 0 1.414s1.024 0.391 1.414 0z"></path>\
</svg>');
--icon-sun-filter: invert(0.61) sepia(0.8) saturate(5) hue-rotate(0deg) brightness(0.92);
--icon-moon: url('data:image/svg+xml,\
<svg version="1.1" xmlns="http://www.w3.org/2000/svg" fill="currentColor" viewBox="0 0 24 24">\
<path d="M21.996 12.882c0.022-0.233-0.038-0.476-0.188-0.681-0.325-0.446-0.951-0.544-1.397-0.219-0.95 0.693-2.059 1.086-3.188 1.162-0.696 0.047-1.399-0.027-2.077-0.226-0.656-0.192-1.29-0.501-1.874-0.932-0.655-0.484-1.181-1.074-1.575-1.729-0.409-0.68-0.676-1.432-0.792-2.206s-0.082-1.571 0.11-2.342c0.184-0.741 0.514-1.46 0.999-2.115 0.142-0.191 0.216-0.435 0.191-0.691-0.053-0.55-0.542-0.952-1.092-0.898-1.117 0.109-2.186 0.399-3.172 0.843-1.005 0.452-1.925 1.065-2.723 1.808-0.883 0.82-1.618 1.801-2.159 2.901-0.523 1.064-0.863 2.238-0.978 3.485-0.125 1.347 0.024 2.658 0.402 3.878 0.392 1.266 1.031 2.431 1.863 3.433s1.86 1.843 3.033 2.461c1.13 0.595 2.392 0.982 3.739 1.106s2.659-0.025 3.878-0.403c1.266-0.392 2.431-1.031 3.433-1.863s1.843-1.86 2.461-3.033c0.595-1.13 0.982-2.392 1.106-3.739zM19.567 14.674c-0.126 0.351-0.276 0.689-0.447 1.014-0.493 0.937-1.166 1.76-1.969 2.427s-1.735 1.178-2.747 1.491c-0.973 0.302-2.021 0.421-3.102 0.321s-2.089-0.41-2.99-0.884c-0.937-0.493-1.76-1.166-2.427-1.969s-1.178-1.735-1.491-2.747c-0.302-0.973-0.421-2.021-0.321-3.102 0.092-1 0.365-1.938 0.782-2.786 0.43-0.878 1.018-1.661 1.725-2.319 0.64-0.595 1.377-1.086 2.183-1.449 0.179-0.081 0.362-0.155 0.548-0.223-0.092 0.257-0.171 0.516-0.236 0.778-0.256 1.029-0.302 2.091-0.147 3.121s0.51 2.032 1.056 2.941c0.527 0.875 1.23 1.663 2.1 2.306 0.775 0.573 1.622 0.986 2.5 1.243 0.907 0.266 1.846 0.364 2.772 0.302 0.752-0.050 1.496-0.207 2.21-0.465z"></path>\
</svg>');
--icon-moon-filter: invert(0.75);
--background: #efefef;
--text-color: #141414;
--button-icon: var(--icon-moon);
--button-icon-filter: var(--icon-moon-filter);
--button-background: var(--color-dark);
--button-color: var(--color-light);
--border-color: var(--color-dark-alpha);
}
prefers-color-scheme
因为我们已经定义了基本的视觉样式（主要是颜色和图标），因此我们需要分别在白昼模式和暗黑模式下分别写两个不同场景下的前端样式，这里要运用css中的prefers-colors-scheme：
body {
background: var(--background);
color: var(--text-color);
transition: background 500ms ease-in-out, color 200ms ease;
}
@media (prefers-color-scheme: dark) {
:root {
--color-mode: 'dark';
}
:root:not([data-user-color-scheme]) {
--background: var(--color-dark);
--text-color: var(--color-light);
--button-icon: var(--icon-sun);
--button-icon-filter: var(--icon-sun-filter);
--button-background: var(--color-light);
--button-color: var(--color-dark);
--border-color: var(--color-light-alpha);
}
}
[data-user-color-scheme='dark'] {
--background: var(--color-dark);
--text-color: var(--color-light);
--button-icon: var(--icon-sun);
--button-icon-filter: var(--icon-sun-filter);
--button-background: var(--color-light-alpha);
--button-color: var(--color-dark);
--border-color: var(--color-light-alpha);
}
因为我们已经默认前端是白昼模式，所以我们需要定义在暗黑模式下的css，:root 下是没有定义data-user-color-scheme 的，这是确保默认值不会覆盖用户的个性化设计。
切换时的按钮样式变化
按钮切换时涉及图标和颜色的变化：
.no-js .user-toggle {
display: none;
}
.user-toggle {
margin: 2rem auto 0 auto;
padding-top: 2.5rem;
max-width: 20rem;
border-top: 1px solid var(--border-color);
text-align: center;
}
.toggle-button {
display: inline-flex;
background: var(--button-background);
color: var(--button-color);
border: none;
font: inherit;
font-size: 1.5rem;
padding: 0.5rem 1rem;
transition: background 500ms ease-in-out, color 200ms ease;
}
.toggle-button__icon {
background: var(--button-icon);
width: 1.2em;
height: 1.2em;
margin: 0 0 0 0.5em;
filter: var(--button-icon-filter);
transform: translateY(1px); /* Optical adjustment */
transition: filter 500ms ease-in-out;
}
.toggle-button:focus {
outline: 1px solid var(--button-background);
outline-offset: 0.5rem;
}
最终的切换的逻辑还是需要JavaScript部分来实现，但是即便没有JavaScript用户依然看到暗黑模式，因为我们定义了.no-js类隐藏了本来的.user-toggle。另外filter可以简单理解成一种颜色对应的反差色。
实现切换的逻辑交互
首先移除.no-js：
document.documentElement.classList.remove('no-js');
然后绑定相关的元素：
const STORAGE_KEY = 'user-color-scheme';
const COLOR_MODE_KEY = '--color-mode';
const modeToggleButton = document.querySelector('.js-mode-toggle');
const modeToggleText = document.querySelector('.js-mode-toggle-text');
const modeStatusElement = document.querySelector('.js-mode-status');
接下来要写两个个工具函数，用来分别提取和加载--color-mode以及user-color-scheme中的各个属性，也就是说当用户切换到白昼模式或者暗黑模式时，对应的前端css样式也是同样的设置：
const getCSSCustomProp = propKey => {
let response = getComputedStyle(document.documentElement).getPropertyValue(propKey);
if (response.length) {
response = response.replace(/\"/g, '').trim();
}
return response;
};
const applySetting = passedSetting => {
let currentSetting = passedSetting || localStorage.getItem(STORAGE_KEY);
if (currentSetting) {
document.documentElement.setAttribute('data-user-color-scheme', currentSetting);
setButtonLabelAndStatus(currentSetting);
} else {
setButtonLabelAndStatus(getCSSCustomProp(COLOR_MODE_KEY));
}
};
当我们进行切换动作的时候，需要有个回调函数打印显示：
const setButtonLabelAndStatus = currentSetting => {
modeToggleText.innerText = `Enable ${currentSetting === 'dark' ? 'light' : 'dark'} mode`;
modeStatusElement.innerText = `Color mode is now "${currentSetting}"`;
};
接下来开始实现切换逻辑：
const toggleSetting = () => {
let currentSetting = localStorage.getItem(STORAGE_KEY);
switch (currentSetting) {
case null:
currentSetting = getCSSCustomProp(COLOR_MODE_KEY) === 'dark' ? 'light' : 'dark';
break;
case 'light':
currentSetting = 'dark';
break;
case 'dark':
currentSetting = 'light';
break;
}
localStorage.setItem(STORAGE_KEY, currentSetting);
return currentSetting;
};
最终绑定点击事件：
modeToggleButton.addEventListener('click', evt => {
evt.preventDefault();
applySetting(toggleSetting());
});
applySetting();
See the Pen dark mode training by Tinc0ist (@WONDERtweet) on CodePen.
其他
- 因为涉及到颜色的对比和反差，这里推荐一款工具 tota11y。
- 浏览器要允许第三方cookie，因为涉及localstorage的临时存储和读取。