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Implementation of absolute positioning reference method

王林

Release： 2024-01-23 08:58:05

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Implementation of absolute positioning reference method

The reference method to achieve absolute positioning requires specific code examples

With the continuous development of web development, the requirements for page layout are getting higher and higher. Absolute positioning is a common layout method that accurately specifies the position of an element on the page. This article will introduce how to achieve absolute positioning through CSS and provide specific code examples.

1. Understand the basic concepts of absolute positioning

Before you start writing code, you first need to understand the basic concepts of absolute positioning. In CSS, absolute positioning determines the position of an element relative to the nearest parent element that has a positioning attribute (the position attribute is not static). If no parent element has a positioning attribute, the element's position will be positioned relative to the browser window.

2. Basic absolute positioning code example

The following is a simple HTML structure example:

<!DOCTYPE html>
<html>
<head>
<style>
#container {
  position: relative;
  width: 400px;
  height: 300px;
}

#box {
  position: absolute;
  top: 50px;
  left: 50px;
  width: 200px;
  height: 150px;
  background-color: red;
}
</style>
</head>
<body>

<div id="container">
  <div id="box"></div>
</div>

</body>
</html>

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In the above example, we created a parent element container and A child element box. The parent element container uses the position: relative attribute, and the child element box uses the position: absolute attribute. And determine the position and size of the sub-element box through the top, left, width and height attributes.

3. Reference method to achieve absolute positioning

In actual development, it is sometimes necessary to use different reference objects to achieve absolute positioning. Two commonly used methods will be introduced here, one is to use the parent element as the reference object, and the other is to use the page boundary as the reference object.

Use the parent element as a reference to achieve absolute positioning

<!DOCTYPE html>
<html>
<head>
<style>
.parent {
  position: relative;
  width: 500px;
  height: 300px;
  border: 1px solid #000;
}

.child {
  position: absolute;
  top: 50px;
  left: 50px;
  width: 200px;
  height: 100px;
  background-color: red;
}
</style>
</head>
<body>

<div class="parent">
  <div class="child"></div>
</div>

</body>
</html>

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In the above code example, we created a parent container parent and a child element child. The parent container parent uses the position: relative attribute, and the child element child uses the position: absolute attribute. Use the top and left attributes to determine the position of the child element relative to the parent container parent.

Use the page boundary as a reference to achieve absolute positioning

<!DOCTYPE html>
<html>
<head>
<style>
.container {
  position: relative;
  width: 500px;
  height: 300px;
  border: 1px solid #000;
}

.box {
  position: absolute;
  top: 50px;
  left: calc(50% - 100px);
  width: 200px;
  height: 100px;
  background-color: red;
}
</style>
</head>
<body>

<div class="container">
  <div class="box"></div>
</div>

</body>
</html>

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In the above code example, we created a container container and an element box. The container container uses the position: relative attribute, and the element box uses the position: absolute attribute. Use the top and left attributes to determine the position of the element box relative to the page boundary. In this example, we use the calc() function to achieve horizontal centering, where calc(50% - 100px) means that the distance between the left side of the element box and the left edge of the page is 50% of the page width minus half the box width.

Summary:

Through the examples of the above two methods, we can achieve absolute positioning using the parent element or page boundary as a reference. These methods are very practical in page layout, and can give full play to the advantages of absolute positioning and accurately control the placement of elements. I hope the introduction in this article can help you.

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