CSS通過邊框border-style來寫小三角，cssborder-style

CSS通過邊框border-style來寫小三角，cssborder-style

<!DOCTYPE html>

/*直接複製代碼即可在瀏覽器驗證*/

<html>

<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        /*盒子的樣式*/
        .box {
            position: relative;
            margin: 20px auto;
            height: 200px;
            width: 200px;
            background: rgba(0, 0, 0, 0.5);
        }
        /*利用border-style實現*/
        .drop-down {
            position: absolute;
            top: 10px;
            left: 10px;
            height: 0;
            width: 0;
            border: 3px;
            /*style依次是上邊框、右、下、左*/
            border-style: solid dashed dashed dashed;
            /*想實現向下的三角就把上邊框設定為實現其餘幾個邊框都是虛線並且顏色設定為透明*/
            border-left-color: transparent;
            border-right-color: transparent;
            border-bottom-color: transparent;
            color: #fff;
        }

        /*再來寫個三角向右的例子*/
        .right {
            position: absolute;
            top: 10px;
            left: 30px;
            height: 0;
            width: 0;
            border:10px;
            border-style:dashed dashed dashed solid;
            border-top-color: transparent;
            border-right-color: transparent;
            border-bottom-color: transparent;
            color: yellowgreen;
        }


    </style>
</head>
<body>
<!--先寫個盒子加上黑色背景，來和產生的小三角來做下對比-->
<div class="box">
    <i class="drop-down"></i>
    <i class="right"></i>
</div>

</body>
</html>