What is flex layout?

Flex elastic layout is a modern web page layout technology. It is based on the Flexbox model of CSS3 and aims to achieve flexible and adaptive web page layout. Flex layout defines the relationship between the container and its internal elements. , which enables web page elements to automatically adjust size, position, and order to accommodate different screen sizes and devices. Its core is to divide the container into two directions: the main axis and the cross axis. The main axis is the main direction of the Flex container, which can be horizontal or vertical, while the cross axis is the direction perpendicular to the main axis.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

Flex elastic layout is a modern web page layout technology, which is based on the Flexbox model of CSS3 and aims to achieve flexible and adaptive web page layout. Flex layout allows web page elements to automatically adjust size, position, and order to adapt to different screen sizes and devices by defining the relationship between the container and its internal elements.

The core of Flex layout is to divide the container into two directions: the main axis and the cross axis. The main axis is the main direction of the Flex container, which can be horizontal (horizontal layout) or vertical (portrait layout), while the cross axis is perpendicular to the main axis. In Flex layout, we can control the layout of the main axis and cross axis by setting the properties of the container.

The main features and properties of Flex layout include:

1. Container properties:

- display: flex; Define a Flex container.

- flex-direction: Set the direction of the main axis, which can be row (horizontal direction), column (vertical direction), row-reverse (reverse horizontal direction), column-reverse (reverse vertical direction).

- flex-wrap: Set whether to wrap, which can be nowrap (no line wrap), wrap (line wrap), wrap-reverse (reverse line wrap).

- justify-content: Set the alignment on the main axis, which can be flex-start (alignment at the starting point), flex-end (alignment at the end), center (alignment in the middle), space-between (alignment at both ends, space-around (equal spacing between items), space-around (equal spacing on both sides of each item).

- align-items: Set the alignment on the cross axis, which can be flex-start (start point alignment), flex-end (end point alignment), center (center alignment), baseline (baseline alignment), stretch (stretch alignment).

2. Element attributes:

- flex: Set the expansion ratio of the element, which can be a number, indicating the proportional relationship of the element when allocating excess space.

- align-self: Sets the alignment of a single element on the cross axis, which can override the align-items property of the container.

- order: Set the display order of elements. The smaller the value, the higher it is.

The advantages and functions of Flex layout include:

1. Flexible layout method: Flex layout provides a flexible layout method, allowing web page elements to automatically adjust the size, position and order to suit Different screen sizes and devices. By simply setting the properties of containers and elements, we can easily achieve complex web page layout effects.

2. Adaptability: Flex layout can automatically adjust the size and position of elements according to the size of the container to adapt to different screen sizes and devices. This means that whether it is a large-screen desktop computer or a small-screen mobile phone, the web page can provide a good user experience.

3. Simplify nested structures: Flex layout can reduce nested structures and simplify HTML code. By setting the properties of containers and elements, we can easily achieve common layout effects such as multi-column layout, vertical centering, and horizontal centering, without using complex CSS techniques and additional HTML structures.

4. Responsive design: Flex layout is very suitable for responsive design, which can automatically adjust the layout according to different screen sizes and devices. By setting the properties of containers and elements, we can achieve responsive design effects such as fluid layout, adaptive navigation, and elastic images, providing a consistent user experience.

5. Scalability and maintainability: Flex layout has good scalability and maintainability. By using Flex layout, we can divide the web page into multiple modules and add, delete and adjust them as needed. In this way, we can develop and maintain web pages more flexibly and improve the readability and maintainability of the code.

In general, Flex elastic layout is a modern web page layout technology. It allows web page elements to automatically adjust the size, position and order to adapt to different screen sizes by setting the properties of containers and elements. and equipment. Flex layout has the advantages of flexible layout, adaptability, simplified nested structure, responsive design, scalability and maintainability. It is an important tool for realizing modern web page layout.

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