:only-of-type

CSS 伪类 :only-of-type 代表了任意一个元素，这个元素没有其他相同类型的兄弟元素。

element:only-of-type { style properties }

HTML

<main>
  <div>I am `div` #1.</div>
  <p>I am the only `p` among my siblings.</p>
  <div>I am `div` #2.</div>
  <div>I am `div` #3.
    <i>I am the only `i` child.</i>
    <em>I am `em` #1.</em>
    <em>I am `em` #2.</em>
  </div>
</main>

CSS

main :only-of-type {
  color: red;
}

结果

• :only-child
• :first-of-type
• :last-of-type
• :nth-of-type