语法
:only-child {
css declarations;
}
:only-child 选择器的例子：
<!DOCTYPE html>
<html>
<head>
<title>文档的标题</title>
<style>
p:only-child {
background: #1c87c9;
}
</style>
</head>
<body>
<h2>:only-child selector example</h2>
<div>
<p>Lorem ipsum is simply dumnmy text.</p>
</div>
<div>
<p>生活终归还得继续。.</p>
<p>生活终归还得继续。.</p>
</div>
</body>
</html>
<li> 标记的 :only-child 选择器示例：
<!DOCTYPE html>
<html>
<head>
<title>文档的标题</title>
<style>
ul li {
list-style-type: square;
}
li:only-child {
color: blue;
list-style-type: disc;
}
</style>
</head>
<body>
<h2>:only-child selector example</h2>
<ol>
<li>
One element
<ul>
<li>This list has just one element.</li>
</ul>
</li>
<li>
Two elements
<ul>
<li>This list has two elements.</li>
<li>This list has two elements.</li>
</ul>
</li>
<li>
Three elements
<ul>
<li>This list has three elements.</li>
<li>This list has three elements.</li>
<li>This list has three elements.</li>
</ul>
</li>
</ol>
</body>
</html>
<em> 标签的 :only-child 选择器示例：
<!DOCTYPE html>
<html>
<head>
<title>文档的标题</title>
<style>
em:only-child {
background-color: #8ebf42;
}
</style>
</head>
<body>
<h2>:only-child selector example</h2>
<p>This is a <em>paragraph</em>.</p>
<p>This is a paragraph.</p>
</body>
</html>
<div> 标签的 :only-child 选择器示例：
<!DOCTYPE html>
<html>
<head>
<title>文档的标题</title>
<style>
div:only-child {
color: #8ebf42;
font-weight: bold;
}
div {
display: block;
margin: 6px;
padding: 5px;
outline: 1px solid #1c87c9;
}
div div {
display: inline-block;
}
</style>
</head>
<body>
<h2>:only-child selector example</h2>
<div>
<div>I am an only child.</div>
</div>
<div>
<div>I am the 1st sibling.</div>
<div>I am the 2nd sibling.</div>
<div>
I am the 3rd sibling,
<div>but this is an only child.</div>
</div>
</div>
</body>
</html>
:only-child 伪选择器匹配一个元素，如果它是其父元素的唯一子元素。
仅当其父元素没有任何类型的其他子元素时才会选择该元素。
:only-child 伪类与 :first-child、:last-child 或者 :nth-child()、:nth-last-child() 相同，但具有较低的特异性。
日期：2020-06-02 22:14:41 来源：oir作者：oir