用纯 CSS 创建一个三角形

参考自网络资料(原文第 4 点)： https://juejin.im/post/5cb92d9a5188254160581b87。

1. 实现方式

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <link rel="stylesheet" type="text/css" href="style.css">
    </head>
    <body>
        <div></div>
    </body>
</html>

引用样式的 html

div{
    width: 0;
    height: 0;
    border-top: 50px solid transparent;
    border-left: 50px solid transparent;
    border-right: 50px solid transparent;
    border-bottom: 50px solid red;
}

2. 一步一步理解创建原理

创建一个正方形，宽高为 100px，背景颜色为黑色

div{
    width: 100px;
    height: 100px;
    background-color: black;
}

设置上边框

div{
    width: 100px;
    height: 100px;
    background-color: black;
    border-top: 50px solid yellow;       
}

设置左边框

div{
    width: 100px;
    height: 100px;
    background-color: black;
    border-top: 50px solid yellow;
    border-left: 50px solid green;    
}

设置右边框

div{
    width: 100px;
    height: 100px;
    background-color: black;
    border-top: 50px solid yellow;
    border-left: 50px solid green;
    border-right: 50px solid blue;    
}

设置下边框

div{
    width: 100px;
    height: 100px;
    background-color: black;
    border-top: 50px solid yellow;
    border-left: 50px solid green;
    border-right: 50px solid blue;
    border-bottom: 50px solid red;      
}

将盒子宽高设置为 0

div{
    width: 0;   
    height: 0;   
    border-top: 50px solid yellow;
    border-left: 50px solid green;
    border-right: 50px solid blue;
    border-bottom: 50px solid red;
}

将上、左、右边框颜色设置为透明 transparent

div{
    width: 0;
    height: 0;
    border-top: 50px solid transparent;
    border-left: 50px solid transparent;
    border-right: 50px solid transparent;
    border-bottom: 50px solid red;
}