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Explore a deep understanding of the syntactic structure of the id selector

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Release： 2024-01-03 09:26:53

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Explore a deep understanding of the syntactic structure of the id selector

In-depth understanding of the syntax structure of the id selector requires specific code examples

In CSS, the id selector is a common selector that is based on HTML elements. The id attribute to select the corresponding element. A deep understanding of the syntactic structure of the id selector can help us better use CSS to select and style specific elements.

The syntax structure of the id selector is very simple. It uses the pound sign (#) plus the value of the id attribute to specify the selected element. For example, if we have an HTML element with an id attribute value of "myElement", we can use the id selector to select this element and style it:

#myElement {
  color: red;
}

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In the above code, we use the id selector Use the tool "#myElement" to select the HTML element with the id "myElement" and set its text color to red.

It should be noted that the id selector is unique, and the id value in each HTML document should be unique and should not appear repeatedly. This is because the id selector will only select the first element that matches the specified id value, ignoring other elements with the same id value. Therefore, when using the id selector, you should ensure that the id is unique.

In addition, the id selector has a higher priority than most other selectors, so it has strong priority. This means that if multiple selectors match the same element but contain an id selector, the style of the id selector will be applied.

The following are some specific code examples to demonstrate the use of id selectors:

<!DOCTYPE html>
<html>
<head>
  <style>
    /* 使用id选择器样式化id为"myElement"的元素 */
    #myElement {
      color: red;
      font-weight: bold;
    }
    
    /* 使用id选择器样式化id为"myBox"的元素 */
    #myBox {
      background-color: yellow;
      border: 1px solid black;
    }
  </style>
</head>
<body>
  <div id="myElement">
    这是一个文本元素。
  </div>
  <div id="myBox">
    这是一个具有背景色和边框的盒子。
  </div>
</body>
</html>

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In the above code, we define two different id selectors, respectively used for styling HTML elements with ids "myElement" and "myBox". By assigning different id attribute values to these elements, we can select and style them.

It should be noted that the id selector only works for HTML elements with the specified id attribute value. If no matching id attribute value is found, the corresponding style will not be applied.

In short, a deep understanding of the syntax structure of the id selector can help us better use CSS to select and style specific HTML elements. By understanding the priority and uniqueness requirements of id selectors, combined with specific code examples, we can apply id selectors more flexibly and achieve the desired style effects.

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