flex兼容性写法

• flex：定义布局为盒模型
• flex-v：盒模型垂直布局
• flex-1：子元素占据剩余的空间
• flex-align-center：子元素垂直居中
• flex-pack-center：子元素水平居中
• flex-pack-justify：子元素两端对齐

.flex { display: -webkit-box; display: -webkit-flex; display: -ms-flexbox; display: flex; }

.flex-v { -webkit-box-orient: vertical; -webkit-flex-direction: column; -ms-flex-direction: column; flex-direction: column; }

.flex-1 { -webkit-box-flex: 1; -webkit-flex: 1; -ms-flex: 1; flex: 1; }

.flex-align-center { -webkit-box-align: center; -webkit-align-items: center; -ms-flex-align: center; align-items: center; }

.flex-pack-center { -webkit-box-pack: center; -webkit-justify-content: center; -ms-flex-pack: center; justify-content: center; }

.flex-pack-justify { -webkit-box-pack: justify; -webkit-justify-content: space-between; -ms-flex-pack: justify; justify-content: space-between; }