CSS变量对JS交互组件开发带来的提升与变革示例代

<label>图片1</label>
<div class="bar" style="--percent: 60;"></div>
<label>图片2</label>
<div class="bar" style="--percent: 40;"></div>
<label>图片3</label>
<div class="bar" style="--percent: 20;"></div>

.bar {
    height: 20px; width: 300px;
    background-color: #f5f5f5;
}
.bar::before {
    display: block;
    counter-reset: progress var(--percent);
    content: counter(progress) '%\2002';
    width: calc(1%  var(--percent));
    color: #fff;
    background-color: #2486ff;
    text-align: right;
    white-space: nowrap;
    overflow: hidden;
}

/
  @author zhangxinxu(.)
  @description 点击页面任意位置，标记坐标位置
 /
document.addEventListener('mousedown', function (event) {
    var target = event.target;
    var body = document.body;
    var html = document.documentElement;

    // 设置自定义属性值
    body.style.setProperty('--pagex', event.pageX);
    body.style.setProperty('--pagey', event.pageY);

    html.style.setProperty('--clientx', event.clientX);
    html.style.setProperty('--clienty', event.clientY);
    html.style.setProperty('--scrolly', window.pageYOffset);

    target.style.setProperty('--offsetx', event.offsetX);
    target.style.setProperty('--offsety', event.offsetY);
    target.parentElement.style.setProperty('--target-width', target.clientWidth);
    target.parentElement.style.setProperty('--target-height', target.clientHeight);
    target.parentElement.style.setProperty('--target-left', target.offsetLeft);
    target.parentElement.style.setProperty('--target-', target.offsetTop);
});

.btn:not([disabled]):active::after {
    transform: translate(-50%,-50%) scale(0);
    opacity: .3;
    transition: 0s;
}
.btn::after {
    content: "";
    display: block;
    position: absolute;
    width: 100%; height: 100%;
    left: var(--x, 0); : var(--y, 0);
    pointer-events: none;
    background: radial-gradient(circle, currentColor 10%, transparent 10.01%) no-repeat 50%;
    transform: translate(-50%,-50%) scale(10);
    opacity: 0;
    transition: transform .3s, opacity .8s;
}

body:active::after {
    transform: translate(-50%, -100%);
    opacity: 0.5;
    transition: 0s;
    left: -999px;
}
body::after {
    content: 'zhangxinxu.';
    position:fixed;
    z-index: 999;
    left: calc(var(--clientx, -999)  1px);
    : calc(var(--clienty, -999)  1px);
    transform: translate(-50%, calc(-100% - 20px));
    opacity: 0;
    transition: transform .3s, opacity .5s;
}

<div class="yw-tab-tab"> 
  <a href="javascript:" class="yw-tab-a">QQ阅读</a>
  <a href="javascript:" class="yw-tab-a">起点读书</a>
  <a href="javascript:" class="yw-tab-a">红袖读书</a>
  <a href="javascript:" class="yw-tab-a">飞读免费小说</a>
</div>

.yw-tab-tab {
    position: relative;
    display: flex;
    max-width: 414px;
    justify-content: space-between;
    border-bottom: 1px solid #717678;
    background-color: #fff;
    margin: 30px auto;
}
.yw-tab-tab::before,
.yw-tab-tab::after {
    position: absolute;
    width: calc(var(--target-width, 0)  1px);
    left: calc(var(--target-left, -299)  1px);
    color: #2a80eb;
}
.yw-tab-tab[style]::before,
.yw-tab-tab[style]::after  {
    content: '';
}
.yw-tab-tab::before {
    background-color: currentColor;
    height: calc(var(--target-height)  1px);
    mix-blend-mode: overlay;
}
.yw-tab-tab::after {
    border-bottom: solid;    
    bottom: -2px;
    transition: left .2s, width .2s;
}
.yw-tab-a {
    color: #717678;
    padding: 10px 0;
}