Explain the importance and function of absolutely positioned elements

To understand the importance and role of absolutely positioned elements, specific code examples are required

Introduction:
In web page layout, we often use absolute positioned elements to Control and adjust the position of elements on the page. Absolute positioning is a very useful layout technique that gives us more flexible control over the position of elements. This article will introduce the importance and role of absolutely positioned elements, and give some specific code examples.

1. What is an absolutely positioned element?
In CSS, absolutely positioned elements determine their position based on their nearest positioned ancestor elements. When an element is set to absolute positioning, it will be separated from the normal document flow, and its position can be determined through the top, right, bottom, and left attributes. Relative to statically positioned elements, the position of an absolutely positioned element is calculated relative to its containing block (usually the parent element or the nearest positioned ancestor element).

2. The importance and role of absolutely positioned elements

1. Free positioning: Using absolute positioning, elements can be placed anywhere on the page, without being restricted by normal document flow. In this way, we can design and layout the page more flexibly and achieve more complex style effects.
2. Overlay effect: By using the z-index attribute, we can create multiple overlapping absolutely positioned elements on the page, and determine their display order through the z-index value. This overlay effect can make the page richer and more diverse, and can effectively handle the hierarchical relationship of elements on the page.
3. Suspended effect: When we need to achieve floating menus, pop-up boxes and other effects, we usually use absolutely positioned elements. By setting the specific position and style of absolutely positioned elements, we can achieve more delicate and interactive page effects.

3. Code example

1. Free positioning:

<style>
  .wrapper {
    position: relative;
    width: 300px;
    height: 200px;
    border: 1px solid #000;
  }
  .absolut-div {
    position: absolute;
    top: 50px;
    left: 50px;
    width: 100px;
    height: 100px;
    background-color: red;
  }
</style>

<div class="wrapper">
  <div class="absolut-div"></div>
</div>

In the above example, .absolut-divThe element uses absolute positioning. By setting the top and left properties, we can place the .absolut-div element anywhere within the .wrapper element.

2. Overlay effect:

<style>
  .box {
    position: relative;
    width: 200px;
    height: 200px;
    border: 1px solid #000;
    overflow: hidden;
  }

  .absolute-div {
    position: absolute;
    top: 50px;
    left: 50px;
    width: 100px;
    height: 100px;
    background-color: red;
    z-index: 2;
  }

  .relative-div {
    position: relative;
    width: 150px;
    height: 150px;
    background-color: blue;
    z-index: 1;
  }
</style>

<div class="box">
  <div class="absolute-div"></div>
  <div class="relative-div"></div>
</div>

In the above example, the .box element is a normal relative positioning container, .absolute- Both the div element and the .relative-div element are absolutely positioned. By setting their z-index properties, we can adjust their stacking order on the page. In this example, the .absolute-div element has a higher z-index value, so it stacks on top of the .relative-div element.

Conclusion:
Through this article’s introduction to the importance and role of absolutely positioned elements, we can understand that using absolutely positioned elements has great flexibility and creativity in web page layout. By using absolutely positioned elements, we can freely position elements and achieve various interactive effects such as overlay effects and floating effects. At the same time, the article also gives specific code examples to help readers better understand the usage and implementation of absolutely positioned elements. Absolute positioning elements are one of the basic techniques that every front-end developer should master. Only by deeply understanding their importance and role and being able to use them skillfully can we better design and build web page layouts.

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