第一种：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.div1 {
width: 300px;
height: 200px;
position: relative;
border: 1px solid #0b7ffe;
}
.div1::before,
.div1::after {
content: "";
position: absolute;
width: 30px;
height: 30px;
animation: div1Ani 1500ms infinite linear;
}
.div1::before {
top: -5px;
left: -5px;
border-top: 1px solid #0b7ffe;
border-left: 1px solid #0b7ffe;
}
.div1::after {
right: -5px;
bottom: -5px;
border-bottom: 1px solid #0b7ffe;
border-right: 1px solid #0b7ffe;
}
@keyframes div1Ani {
0% {
width: 30px;
height: 30px;
}
50% {
width: calc(100% + 9px);
height: calc(100% + 9px);
}
100% {
width: 30px;
height: 30px;
}
}
</style>
</head>
<body>
<div class="div1">
通过before，after设置对角两个div，并且设置对应的两个边框。
hover改变before，after的大小，并设置过渡，达到最终效果
</div>
</body>
</html>
第二种
.div2 {
width: 300px;
height: 200px;
background: linear-gradient(90deg, #333 50%, transparent 0) repeat-x,
linear-gradient(90deg, #333 50%, transparent 0) repeat-x,
linear-gradient(0deg, #333 50%, transparent 0) repeat-y,
linear-gradient(0deg, #333 50%, transparent 0) repeat-y;
background-size: 10px 2px, 10px 2px, 2px 10px, 2px 10px;
background-position: 0 0, 0 100%, 0 0, 100% 0;
animation: div2Ani 500ms infinite linear;
}
@keyframes div2Ani {
100% {
background-position: 10px 0, -10px 100%, 0 -10px, 100% 10px;
}
}
<div class="div2">
通过设置背景过渡颜色实现虚线，通过background-size控制虚线宽度大小。
background-position指定4条背景的位置。
通过动画设置background-position达到运动效果
</div>
第三种
.div3 {
width: 300px;
height: 200px;
position: relative;
overflow: hidden;
}
.div3::after {
content: '';
position: absolute;
left: -50%;
top: -50%;
width: 200%;
height: 200%;
background-repeat: no-repeat;
background-size: 50% 50%, 50% 50%;
background-position: 0 0, 100% 0, 100% 100%, 0 100%;
background-image: linear-gradient(#399953, #399953), linear-gradient(#fbb300, #fbb300), linear-gradient(#d53e33, #d53e33), linear-gradient(#377af5, #377af5);
animation: div3Rotate 4s linear infinite;
}
.div3 > div {
position: absolute;
left: 5px;
top: 5px;
width: calc(100% - 10px);
height: calc(100% - 10px);
background: #ffffff;
z-index: 2;
padding: 20px;
box-sizing: border-box;
}
@keyframes div3Rotate {
100% {
transform: rotate(360deg);
}
}
<div class="div3">
<div>
大盒子超出隐藏，利用伪类设置背景颜色，通过动画旋转，
并在盒子里面设置一个遮罩层，遮罩层比大盒子小，露出边框达到效果
</div>
</div>
第四种
.div4 {
width: 300px;
height: 200px;
overflow: hidden;
position: relative;
}
.div4::before {
content: '';
position: absolute;
left: -50%;
top: -50%;
width: 200%;
height: 200%;
background-color: #e5e3e3;
background-repeat: no-repeat;
background-position: 0 0;
background-image: conic-gradient(transparent, #343434, transparent 30%);
animation: div4Rotate 4s linear infinite;
}
.div4 > div {
position: absolute;
left: 5px;
top: 5px;
width: calc(100% - 10px);
height: calc(100% - 10px);
background: #ffffff;
z-index: 2;
padding: 20px;
box-sizing: border-box;
}
@keyframes div4Rotate {
100% {
transform: rotate(360deg);
}
}
<div class="div4">
<div>
大盒子超出隐藏，利用伪类设置背景颜色过渡，通过动画旋转，
并在盒子里面设置一个遮罩层，遮罩层比大盒子小，露出边框达到效果
</div>
</div>
第五种
.div5 {
width: 300px;
height: 200px;
position: relative;
color: #fff;
border: 2px solid gold;
border-radius: 10px;
background: #ffd700;
transition: all .3s;
}
.div5::before {
content: "";
position: absolute;
top: -10px;
left: -10px;
right: -10px;
bottom: -10px;
border: 2px solid #ffd700;
border-radius: 10px;
animation: div5Ani 3s infinite linear;
}
.div5::after {
content: "";
position: absolute;
top: -10px;
left: -10px;
right: -10px;
bottom: -10px;
border: 2px solid #ffd700;
border-radius: 10px;
animation: div5Ani 3s infinite linear;
}
@keyframes div5Ani {
0%,
100% {
clip-path: inset(0 0 98% 0);
}
25% {
clip-path: inset(0 98% 0 0);
}
50% {
clip-path: inset(98% 0 0 0);
}
75% {
clip-path: inset(0 0 0 98%);
}
}
.div5::after {
animation: div5Ani 3s infinite -1.5s linear;
}
<div class="div5">
通过clip-path属性，对伪类进行裁剪，而伪类是支持圆角边框的，通过规则的动画去裁剪，达到运动效果
</div>
第六种
.div6{
width: 300px;
height: 200px;
position: relative;
margin: auto;
overflow: hidden;
border: 5px solid;
border-image: linear-gradient(45deg, gold, deeppink) 1;
clip-path: inset(0px round 5px);
animation: div6Ani 3s infinite linear;
filter: hue-rotate(360deg);
}
@keyframes div6Ani {
0% {
filter: hue-rotate(0deg);
}
100% {
filter: hue-rorate(360deg);
}
}
<div class="div6">
边框border-image属性，颜色过渡，设置过渡动画，色调旋转滤镜，裁剪圆角，达到最终效果
</div>
