【CSS】设置0.5px的边框宽度

直接写border: 0.5px solid red; 这样在移动端可能会出现问题，下面说下解决办法：

直接上代码：

<!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>
        .divClass {
            width: 100px;
            height: 100px;
            background-color: aquamarine;
            position: relative;
            margin-bottom: 20px;
            border-radius: 6px;
            /* border: 0.5px solid red; */
        }

        /* 方法1:上下左右都-50%，边框宽度和圆角都得扩大2倍，然后再用scale进行缩放 */
        .border1:after {
            content: '';
            position: absolute;
            top: -50%;
            bottom: -50%;
            left: -50%;
            right: -50%;
            border: 1px solid red;
            border-radius: 12px;
            -webkit-transform: scale(0.5);
            transform: scale(0.5);
        }

        /* 方法2:宽高都扩大两倍，然后再用scale进行缩放 */
        .border2:after {
            content: '';
            display: block;
            position: absolute;
            left: 0;
            top: 0;
            box-sizing: border-box;
            width: 200%;
            height: 200%;
            border: 1px solid red;
            border-radius: 12px;
            -webkit-transform: scale(0.5);
            transform: scale(0.5);
            transform-origin: 0 0;
        }

        .border3::after {
            /* 方法1： */
            content: "";
            display: block;
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            height: 1px;
            background-color: red;
            -webkit-transform: scaleY(0.5);
            transform: scaleY(0.5);
            transform-origin: 0 0;

            /* 方法2： */
            /* content: "";
            display: block;
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 1px;
            background-color: red;
            -webkit-transform: scaleY(0.5);
            transform: scaleY(0.5);
            transform-origin: 0 0; */
        }
    </style>
</head>

<body>
    <div class="divClass border1">我有个0.5px的四条边框</div>
    <div class="divClass border2">我有个0.5px的四条边框</div>

    <div class="divClass border3">我有个0.5px的上边框</div>
</body>

</html>

在浏览器运行截图如下：