Why Does `:first-child` Fail to Select the First `` in Nested Elements, and How Can I Fix It?-CSS Tutorial-php.cn

Why Does `:first-child` Fail to Select the First `` in Nested Elements, and How Can I Fix It?

Barbara Streisand

Release： 2024-12-09 10:12:08

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Why Does `:first-child` Fail to Select the First `` in Nested Elements, and How Can I Fix It?

:first-child Fails to Match Expected Elements in Certain Cases

When attempting to select the first h1 element within a div with the class "detail_container," the :first-child selector may not work as intended. This occurs when the h1 is not the immediate child of the div, as in the following example:

<style type="text/css">
.detail_container h1:first-child {
  color: blue;
} 
</style>
<body>
<div class="detail_container">
  <ul>
    <li></li>
    <li></li>
  </ul>
  <h1>First H1</h1>
  <h1>Second H1</h1>
</div>
</body>

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In this case, the :first-child selector fails to select the first h1 because the ul element is the first child of the div, not the h1.

How to Resolve the Issue

To select the first h1 element regardless of its position within the div, there are alternative CSS selectors available:

1. :first-of-type

The :first-of-type selector selects the first child of its parent that matches a given element type. In this case, it would select the first h1 child of the div, as follows:

.detail_container h1:first-of-type {
  color: blue;
}

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2. Class-based Selection

Another approach is to give the first h1 a unique class, such as "first," and then target that class in the CSS:

.detail_container h1.first {
  color: blue;
}

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This method provides greater flexibility and control over the selection.

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