九个纯 CSS 实现的 Loading 效果

作者：Jimmy
https://juejin.cn/post/7080542771387301896

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为保证运行正常，咱先规定下:

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* {
  box-sizing: border-box;
}

一、平滑加载

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<div class="progress-1"></div>

.progress-1 {
  width:120px;
  height:20px;
  background:
   linear-gradient(#000 0 0) 0/0% no-repeat
   #ddd;
  animation:p1 2s infinite linear;
}
@keyframes p1 {
    100% {background-size:100%}
}

linear-gradient(#000 0 0) 你可以理解为 linear-gradient(#000 0 100%)，如果还不熟悉，复制 linear-gradient(#000 0 50%, #f00 50% 0) ，替换原先的部分跑一下。觉得 linear-gradient(#000 0 0) 别扭的话，直接写 #000 即可。
0/0% 是 background-position: 0;/background-size: 0; 的简写。

二、按步加载

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<div class="progress-2"></div>

.progress-2 {
  width:120px;
  height:20px;
  border-radius: 20px;
  background:
   linear-gradient(orange 0 0) 0/0% no-repeat
   lightblue;
  animation:p2 2s infinite steps(10);
}
@keyframes p2 {
    100% {background-size:110%}
}

steps(10) 是 step(10, end) 的简写，指明刚开始没有，所以有第2点的处理
100% {background-size:110%} 添加多一个 step 的百分比，上面的 step 是 10，所以是100% + (1/10)*100% = 110%

三、条纹加载

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<div class="progress-3"></div>

.progress-3 {
  width:120px;
  height:20px;
  border-radius: 20px;
  background:
   repeating-linear-gradient(135deg,#f03355 0 10px,#ffa516 0 20px) 0/0% no-repeat,
   repeating-linear-gradient(135deg,#ddd 0 10px,#eee 0 20px) 0/100%;
  animation:p3 2s infinite;
}
@keyframes p3 {
    100% {background-size:100%}
}

repeating-linear-gradient(135deg,#ddd 0 10px,#eee 0 20px) 0/100%; 画出灰色的斑马线条纹，repeating-linear-gradient(135deg,#f03355 0 10px,#ffa516 0 20px) 0/0% no-repeat 则是进度条加载的条纹。

四、虚线加载

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<div class="progress-4"></div>

.progress-4 {
  width:120px;
  height:20px;
  -webkit-mask:linear-gradient(90deg,#000 70%,#0000 0) 0/20%;
  background:
   linear-gradient(#000 0 0) 0/0% no-repeat
   #ddd;
  animation:p4 2s infinite steps(6);
}
@keyframes p4 {
    100% {background-size:120%}
}

-webkit-mask 默认有值 repeat，不然遮罩不会有五个

五、电池加载

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<div class="progress-5"></div>

.progress-5 {
  width:80px;
  height:40px;
  border:2px solid #000;
  padding:3px;
  background: 
    repeating-linear-gradient(90deg,#000 0 10px,#0000 0 16px) 
    0/0% no-repeat content-box content-box;
  position: relative;
  animation:p5 2s infinite steps(6);
}
.progress-5::before {
  content:"";
  position: absolute;
  top:-2px;
  bottom:-2px;
  left:100%;
  width:10px;
  background:
    linear-gradient(
        #0000   calc(50% - 7px),#000 0 calc(50% - 5px),
        #0000 0 calc(50% + 5px),#000 0 calc(50% + 7px),#0000 0) left /100% 100%,
    linear-gradient(#000 calc(50% - 5px),#0000 0 calc(50% + 5px),#000 0) left /2px 100%,
    linear-gradient(#0000 calc(50% - 5px),#000 0 calc(50% + 5px),#0000        0) right/2px 100%;
  background-repeat:no-repeat;
}

六、内嵌加载

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<div class="progress-6"></div>
.progress-6 {
  width:120px;
  height:22px;
  border-radius: 20px;
  color: #514b82;
  border:2px solid;
  position: relative;
}
.progress-6::before {
  content:"";
  position: absolute;
  margin:2px;
  inset:0 100% 0 0;
  border-radius: inherit;
  background: #514b82;
  animation:p6 2s infinite;
}
@keyframes p6 {
    100% {inset:0}
}

inset:0 100% 0 0; 右边内缩 100%，所以在 keyframes 部分需要将 inset 设置为 0。

七、条纹加载

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<div class="progress-8"></div>

.progress-8 {
  width:60px;
  height:60px;
  border-radius: 50%;
  -webkit-mask:linear-gradient(0deg,#000 55%,#0000 0) bottom/100% 18.18%;
  background:
   linear-gradient(#f03355 0 0) bottom/100% 0% no-repeat
   #ddd;
  animation:p8 2s infinite steps(7);
}
@keyframes p8 {
    100% {background-size:100% 115%}
}

对 linear-gradient 描绘的角度做调整，再加上蒙版。

八、水柱加载

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<div class="progress-9"></div>
.progress-9 {    
  --r1: 154%;
  --r2: 68.5%;
  width:60px;
  height:60px;
  border-radius: 50%; 
  background:
    radial-gradient(var(--r1) var(--r2) at top ,#0000 79.5%,#269af2 80%) center left,
    radial-gradient(var(--r1) var(--r2) at bottom,#269af2 79.5%,#0000 80%) center center,
    radial-gradient(var(--r1) var(--r2) at top ,#0000 79.5%,#269af2 80%) center right,
    #ccc;
  background-size: 50.5% 220%;
  background-position: -100% 0%,0% 0%,100% 0%;
  background-repeat:no-repeat;
  animation:p9 2s infinite linear;
}
@keyframes p9 {
    33%  {background-position:    0% 33% ,100% 33% ,200% 33% }
    66%  {background-position: -100%  66%,0%   66% ,100% 66% }
    100% {background-position:    0% 100%,100% 100%,200% 100%}
}

九、信号加载

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<div class="progress-10"></div>
.progress-10 {
  width:120px;
  height:60px;
  border-radius:200px 200px 0 0;
  -webkit-mask:repeating-radial-gradient(farthest-side at bottom ,#0000 0,#000 1px 12%,#0000 calc(12% + 1px) 20%);
  background:
   radial-gradient(farthest-side at bottom,#514b82 0 95%,#0000 0) bottom/0% 0% no-repeat
   #ddd;
  animation:p10 2s infinite steps(6);
}
@keyframes p10 {
    100% {background-size:120% 120%}
}

参考资料

原文： 10 CSS-only loaders ready to use!: