flex Layout is the most frequently used and outstanding function in css3. It is a bit complicated. It is divided into attributes applied to the container and attributes on the project, that is, on the parent element. of and attributes on child elements.
display: flex
<style>p{display: flex; background-color: yellow;}b{background-color: red;}</style><body> <p> <b>a</b><b>b</b><b>c</b><b>d</b><b>e</b><b>f</b><b>g</b><b>h</b><b>i</b> </p></body>When the parent element is set to flex After, its parent element itself will appear as a block-level element. If you want to appear as an inline element, you can use inline-flex. All child elements, whether block-level or inline, will immediately become inline layout. This is due to the default values of other attributes and can be modified later.
<style>p{display: flex; background-color: yellow; margin: 5px;}p.row{ flex-direction: row;}p.row-reverse{ flex-direction: row-reverse;}p.column{ flex-direction: column;}p.column-reverse{ flex-direction: column-reverse;}b{background-color: red;}</style><body> <p class="row"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="row-reverse"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="column"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="column-reverse"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body>flex-direction Decision Arrangement direction of child elements, default value row.
<style>p{display: flex; background-color: yellow; margin: 5px; }p.nowrap{ flex-wrap: nowrap;}p.wrap{ flex-wrap: wrap;}p.wrap-reverse{ flex-wrap: wrap-reverse;}b{background-color: red; width: 100px;}</style><body> <p class="nowrap"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="wrap"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="wrap-reverse"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body> Determines how the child element should be handled when it exceeds one line. The default value nowrap will compress the width of child elements, wrap will wrap a new line, and wrap-reverse will add a new line upwards. Note: This is discussed under the premise that the main axis is the X-axis.
<style>b{background-color: red; }p{display: flex; background-color: yellow; margin: 5px; }p.start{ justify-content: flex-start;}p.end{justify-content: flex-end;}p.center{ justify-content: center;}p.space-between{ justify-content: space-between;}p.space-around{ justify-content: space-around;}</style><body> <p class="start"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="end"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="center"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="space-between"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="space-around"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body>justify-content
Determines whether the child element is on the main axis (currently the X axis ), the default value isflex-start. The distance between space-between and space-around is divided equally by the excess space, but the latter will also count the space for the left and right ends.
##align-items
<style>b{background-color: red; width: 40px;}b:nth-child(1){}b:nth-child(2){font-size: 30px; height: 40px;}b:nth-child(3){height: 50px;}b:nth-child(4){height: 60px;}p{display: flex; flex-wrap: wrap; background-color: yellow; margin: 5px; }p.start{ align-items: flex-start;}p.end{ align-items: flex-end;}p.center{ align-items: center;}p.baseline{ align-items: baseline;}p.stretch{ align-items: stretch;}</style><body> <p class="start"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="end"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="center"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="baseline"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="stretch"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body>Determine the secondary axis (currently the Y axis) The alignment of elements. The default value
stretch means that when the child element does not set a height, it will fill the height of the parent class.
align-content
<style>b{background-color: red; width: 100px;}p{display: flex; flex-wrap: wrap; background-color: yellow; margin: 5px; height: 70px;}p.start{ align-content: flex-start;}p.end{ align-content: flex-end;}p.center{ align-content: center;}p.space-between{ align-content: space-between;}p.space-around{ align-content: space-around;}p.stretch{ align-content: stretch;}</style><body> <p class="start"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="end"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="center"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="space-between"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="space-around"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="stretch"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body>indicates that when the child element has multiple lines, each line Position on the secondary axis (currently the Y axis). The default value
stretch means changing the height of each row of child elements until the parent element is filled.
Attributes on child elements
<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; }b.test{order: -1;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>means arranging elements of the same level from small to large, the default value is
0.
##flex-grow
<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; }b.test{flex-grow: 1; background-color: green;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>0
, which means it does not occupy space. The current space bisection ratio is0 : 0 : 1 : 0, so c occupies all remaining space.
<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; width: 100px; flex-shrink: 0;}b.test{flex-shrink: 1; background-color: green;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>
flex-shrink, which means
1 : 1 : 1 : 1, that is, equal-ratio compression. The current ratio is 0: 0: 1: 0, indicating that all space is compressed by c. ##flex-basis
<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; flex-grow: 1;}b.test{flex-basis: 100px; background-color: green;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>
flex-basis
height
. The default valueauto means equal to width or height. ##align-self
<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; flex-grow: 1;}b:nth-child(1){height: 20px;}b:nth-child(2){height: 40px;}b:nth-child(3){height: 50px;}b:nth-child(4){height: 60px;}b.test{align-self: flex-end; background-color: green;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>align-self 表示当前元素可以覆盖父元素 align-items 所决定的副轴（当前为Y轴）上的方向。默认 auto，即不设置。可选择与 align-items 一致，auto | flex-start | flex-end | center | baseline | stretch 。
flex-direction:row 作为子元素排序方向为基础。如果改为 flex-direction:column ，主轴将为变成 Y 轴，而副轴将变成 X 轴，所有属性的效果将会改变，这个留给读者自行实践。
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