css 垂直居中

1、absolute + transform

.wp {
  border: 1px solid red;
  width: 300px;
  height: 300px;
  position: relative;
}

.box {
  background: green;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  /* transform移动自身 */
}

2、absolute + margin:auto

• 必须定 width、height
• 否则，内部width、height等于外部宽、高

.wp {
  border: 1px solid red;
  width: 300px;
  height: 300px;
  position: relative;
}

.box {
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  /* 必须定义 width、height，否则全部覆盖 */
  width: 100px;
  height: 100px;
  background-color: powderblue;
}

3、display: table-cell

.wp {
  border: 1px solid red;
  width: 300px;
  height: 300px;

  display: table-cell;
  text-align: center;
  vertical-align: middle;
}

.box {
  width: 100px;
  height: 100px;
  border: 1px solid blue;
  display: inline-block;
}

4、display：flex

.wp {
  border: 1px solid red;
  width: 300px;
  height: 300px;

  display: flex;
  justify-content: center;
  align-items: center;
}

.box {
  /* width、height：可有可无 */
  height: 100px;
  width: 100px;
  border: 1px solid blue;
}

5、display: grid

.wp {
  border: 1px solid red;
  width: 300px;
  height: 300px;
  display: grid;
}

.box {
  justify-self: center;
  align-self: center;
  background-color: powderblue;
}