CSS absolute positioning attribute analysis: absolute and fixed

Absolute positioning is a common and useful layout technology in CSS, by usingposition: absoluteorposition: fixedattribute, which can detach an element from the normal document flow and position it relative to its containing element. This article will analyze the two absolute positioning properties of absolute and fixed in detail and provide specific code examples.

1. position: absolute

The position: absoluteproperty positions an element relative to its nearest positioned ancestor element , if the ancestor element is not positioned, it is positioned relative to the root element of the document.

Basic syntax:

position: absolute; top: 像素值/百分比值; left: 像素值/百分比值; right: 像素值/百分比值; bottom: 像素值/百分比值;

Code example:

In the above example, we created a container element.containerand positioned it The mode is set toposition: relative. Then, create a.boxelement inside the container and set its positioning mode toposition: absolute, passingtopandleftAttribute sets its position to 50 pixels relative to the.containerelement.

2. position: fixed

position: fixedThe attribute positions the element relative to the viewport, regardless of the The scroll bar changes its position as it scrolls.

Basic syntax:

position: fixed; top: 像素值/百分比值; left: 像素值/百分比值; right: 像素值/百分比值; bottom: 像素值/百分比值;

Code example:

 
 
固定头部
 
 
  

In the above example, we created a.headerelement and positioned it as Set toposition: fixed, and set its position to the upper left corner of the viewport through thetopandleftproperties. In this way, the.headerelement will always be displayed at the top of the page and will not be affected by scrolling.

It should be noted that absolutely positioned elements need to have relatively positioned ancestor elements as a reference, while fixedly positioned elements are positioned relative to the viewport.

The absolute positioning attribute is one of the important tools for implementing layout in CSS, which can help us achieve a more flexible and precise page layout. Mastering the usage ofposition: absoluteandposition: fixed, we can better control the position and behavior of page elements.

To summarize,position: absolutepositions the element relative to the nearest positioned ancestor element, whileposition: fixedpositions the element relative to the viewport. These two attributes are widely used in front-end development and provide convenience for us to achieve various layout effects.

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