flex 常见值效果展示
默认值 flex: initial 相当于 flex: 0 1 auto
item 1
item 2 flex initial
item 3
flex: auto 相当于 flex:1 1 auto
item 1
item 2 has flex property
item 3
flex: none 相当于 flex: 0 0 auto;
item 1
item 2 has flex property,no shrink
item 3
flex: 2 相当于 flex: 2 1 0
item 1
item 2 has flex property
item 3