www.w3cschool.cn/css3/2h6g5x…
flex-direction: row | row-reverse | column | column-reverse
justify-content: flex-start | flex-end | center | space-between | space-around
align-items: flex-start | flex-end | center | baseline | stretch
flex-wrap: nowrap|wrap|wrap-reverse|initial|inherit;
align-content: flex-start | flex-end | center | space-between | space-around | stretch
属性设置弹性容器内弹性子元素的属性:
order:用整数值来定义排列顺序，数值小的排在前面。可以为负值。
flex：0 0 100px;
flex：none | [ flex-grow ] || [ flex-shrink ] || [ flex-basis ]
各个值解析:
none：none关键字的计算值为: 0 0 auto
[ flex-grow ]：定义弹性盒子元素的扩展比率。
[ flex-shrink ]：定义弹性盒子元素的收缩比率。
[ flex-basis ]：定义弹性盒子元素的默认基准值。
