水平居中
- 行内元素:
text-align: center - 块级元素:
margin: 0 auto - position:absolute +left:50%+ transform:translateX(-50%)
display:flex + justify-content: center
垂直居中
- 设置line-height 等于height
- position：absolute +top:50%+ transform:translateY(-50%)
display:flex + align-items: center- display:table+display:table-cell + vertical-align: middle;