30秒学会 CSS 片段 – Focus Within

Changes the appearance of a form if any of its children are focused.

• The psuedo class :focus-within applies styles to a parent element if any child element gets focused. For example, an input element inside a form element.

预览

HTML

<form>
  <label for="username">Username:</label>
  <input id="username" type="text" />
  <br />
  <label for="password">Password:</label>
  <input id="password" type="text" />
</form>

CSS

form {
  border: 2px solid #52B882;
  padding: 8px;
  border-radius: 2px;
}

form:focus-within {
  background: #7CF0BD;
}

label {
  display: inline-block;
  width: 72px;
}

input {
  margin: 4px;
}

翻译自：https://www.30secondsofcode.org/css/s/focus-within