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Detailed analysis of HTML fixed positioning principle

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Release： 2024-01-20 08:44:12

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Detailed analysis of HTML fixed positioning principle

In-depth analysis of the implementation principle of HTML fixed positioning requires specific code examples

Introduction:
In web development, we often encounter the need to The element needs to be fixed at a certain position on the page and remain in position as the page scrolls. This is HTML fixed positioning. This article will deeply analyze the implementation principle of HTML fixed positioning and provide specific code examples for readers' reference.

1. The basic concept of HTML fixed positioning
HTML fixed positioning is a special positioning method. By setting the positioning attribute of an element to "fixed", the element can be separated from the document flow and relative to the document flow. The browser window is positioned. Its characteristics are as follows:

The element does not scroll with the scroll bar and always remains at the specified position. The
element is not affected by the layout of other elements and will not affect the position of other elements.

2. The implementation principle of HTML fixed positioning
The implementation principle of fixed positioning can be summarized into the following steps:

Set the positioning attribute of the element to "fixed" ".
Set the left, top, right, and bottom attributes of the element to determine the position of the element relative to the browser window.
When the page scrolls, the position of the element is updated in time by listening to the scroll event.

Code example:

<!DOCTYPE html>
<html>
<head>
  <style>
    #fixed-element {
      position: fixed;
      top: 100px;
      right: 100px;
      width: 200px;
      height: 200px;
      background-color: #f1f1f1;
      border: 1px solid #ddd;
    }
  </style>
</head>
<body>
  <div id="fixed-element">这是一个固定定位的元素</div>
  <div style="height: 2000px; background-color: #ccc;"></div>

  <script>
    window.addEventListener('scroll', function() {
      var element = document.getElementById('fixed-element');
      var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
      element.style.top = 100 + scrollTop + 'px';
    });
  </script>
</body>
</html>

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In the above code example, by setting the style of #fixed-element in the style tag, set its positioning attribute to fixed, and pass top and left Property determines its position relative to the browser window. Then by listening to the scroll event, obtain the scrollTop distance of the page scroll, and update the top attribute of the element so that it always remains at the specified position.

Summary:
Through the above detailed analysis and code examples, we have an in-depth understanding of the implementation principle of HTML fixed positioning. Mastering this principle, we can flexibly use fixed positioning techniques to achieve more dynamic and rich page effects. I hope the content of this article will be helpful to readers.

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