CSS实现子元素水平垂直居中的6种方式

1. flexbox

.parent {
  display: flex;
  justify-content: center;
  align-items: center;
  width: xxxpx;
  height: xxxpx;
}

.child {
  width: xxxpx;
  height: xxxpx;
}

2. grid

    .parent {
      display: grid;
      place-items: center;
      width: xxxpx;
      height: xxxpx;
    }
    .child {
      width: xxxpx;
      height: xxxpx;
    }

3. table-cell

.parent {
  display: table-cell;
  width: xxxpx;
  height: xxxpx;
  vertical-align: middle;
  text-align: center;
}
.child {
  display: inline-block;
  width: xxxpx;
  height: xxxpx;
}

4. 定位+translate

.parent {
  position:  relative;
  width: xxxpx;
  height: xxxpx;
}
.child {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

5. 定位 + margin（负值）

.parent {
  position: relative;
  width: xxxpx;
  height: xxxpx;
}

.child {
  position: absolute;
  top: 50%;
  left: 50%;
  width: wpx;
  heigth: hpx;
  margin-left: w/2 px;
  margin-top: h/2 px;
}

6. 定位 + margin（auto）

.parent {
  position: relative;
  width: xxxpx;
  height: xxxpx;
}

.child {
  position: absolute;
  width: xxxpx;
  height: xxxpx;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  margin: auto;
}