css簡單實現帶箭頭的邊框

原文地址 https://tianshengjie.cn/artic...

css簡單實現帶箭頭的邊框

普通邊框

<style>
    .border {
        width: 100px;
        height: 50px;
        border: 1px solid red;
    }
</style>
<div class="border"></div>

實現由四個三角形組成的正方形

<style>
    .triangle {
        width: 0;
        height: 0;
        border: 100px solid red;
        border-right-color: green;
        border-left-color: blue;
        border-top-color: black;
    }
</style>
<div class="triangle"></div>

向下三角形

<style>
    .triangle-bottom {
        width: 0;
        height: 0;
        border: 100px solid transparent;
        border-top-color: red;
    }
</style>
<div class="triangle-bottom"></div>

將左右下邊顏色設置爲透明 transparent，獲得向下的箭頭

將三角形放入邊框中

<style>
    .border-triangle {
        width: 100px;
        height: 50px;
        border: 1px solid red;
        position: relative;
    }

    .border-triangle:before {
        content: "";
        position: absolute;
        width: 0;
        height: 0;
        border: 4px solid transparent;
        border-top-color: red;
        left: 50%;
        margin-left: -4px;
        bottom: -8px;
    }
</style>
<div class="border-triangle"></div>

將三角形設置爲絕對定位，利用margin-left和left 定位到元素中間，bottom設置-8px，靠近邊框底部居中

帶箭頭的邊框

<style>
    .border-triangle-bottom {
        width: 100px;
        height: 30px;
        border: 1px solid #1d9cd6;
        position: relative;
        border-radius: 4px;
    }

    .border-triangle-bottom:after,
    .border-triangle-bottom:before {
        content: "";
        position: absolute;
        width: 0;
        height: 0;
        border: 4px solid transparent;
        border-top-color: #1d9cd6;
        left: 50%;
        margin-left: -4px;
        bottom: -8px;
    }

    .border-triangle-bottom:after {
        border-top-color: #fff;
        bottom: -7px;
    }
</style>
<div class="border-triangle-bottom"></div>

將邊框顏色換成好看的藍色，將before和after僞元素都設置爲絕對定位，定位到邊框底部劇中，將after僞元素設置成白色，底部偏移量大於before 1px，遮住三角形底部的顏色。這樣一個好看的箭頭邊框就實現了