CSS doesn't take up space: an important concept a front-end developer must understand

With the continuous development of Web front-end technology, more and more functions and effects are added to web pages, and more and more people are getting involved in Web front-end development. Among them, CSS (Cascading Style Sheets) is a very important technology, which is widely used in various aspects such as layout, style, animation and interaction of web pages. However, many developers may not fully understand an important concept of CSS "does not occupy position" (position is not static). This article will explain this in detail.

1. What is CSS that does not occupy position?

CSS does not occupy position is a characteristic of CSS, which means that when an element is set with a non-static positioning attribute (such as absolute, fixed, relative), the element will no longer occupy the document flow. position, that is to say, other elements are no longer arranged according to the position of this element, but directly ignore this element and continue to arrange other elements.

2. The relationship between CSS not occupying position and document flow

Before understanding the role of CSS not occupying position, you need to understand the document flow first. Document flow refers to a standard way of arranging elements in a Web page. Elements are arranged on the page one by one in order from top to bottom and from left to right. Document flow is the basis of Web layout. If elements do not set positioning attributes, they will float on the page according to document flow, affecting and arranging each other.

CSS does not occupy position because of this. When an element in the layout is set with a positioning attribute, it "stands out" from the document flow and is no longer ranked in the document flow, dominating the arrangement of other elements.

3. The role of CSS that does not occupy position

3.1. Implement absolute positioning of elements

When we need to make an element absolute relative to the parent element When positioning, you can use the CSS feature of not occupying position (for example, using position: absolute;). Because the element's positioning is now calculated based on the position of its containing block rather than its position in the document flow, the element's position, size, transparency, and other parameters can be precisely controlled.

3.2. Implement coverage of other elements

Using CSS without occupying position, you can absolutely position an element on top of other elements to block or cover other elements. This feature is very useful when implementing effects such as pop-up layers and image masks.

3.3. Realize the impact on other elements

CSS elements that do not occupy a position will no longer be disturbed by other elements in their position. In other words, you can set the positioning attribute so that the elements are not restricted by the frame and can easily "shuttle" between other elements to achieve refined layout.

4. FAQ about CSS not occupying position

4.1. After an element is set to absolute positioning, will it occupy the position of the document?

Won't. When an element is set with a positioning attribute that is not static, it will no longer occupy the position of the document flow. That is to say, other elements will no longer be arranged according to the position of the element, but will directly ignore this element. This is also the important feature of CSS that does not occupy position.

4.2. How does the browser render CSS elements that do not occupy position?

CSS elements that do not occupy a position will be separated from the normal document flow. Therefore, the browser will treat it as a floating state and calculate and render it separately.

4.3. If you want an element to use position-free features, what CSS styles should be set?

Set the position attribute of the element to not be static. Correspondingly, set the top, bottom, left, right and other attributes to determine the precise position of the element.

5. Summary

CSS does not occupy position is a very important concept in Web front-end development. It can help us achieve many detailed effects and control the position of elements. Thereby improving the interactive experience and visual effects of the web page. However, you also need to pay attention when using CSS not to occupy space. You must set it according to the specific situation to avoid problems such as confusing layout or repeated covering of elements. I hope this article will be helpful to developers learning CSS.

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