元素垂直居中的常见方法

    
　　<--HTML-->
　　<div class="box box1">
        <div>flex</div>
    </div>
    <div class="box box2">
        <div>inline-block</div>
    </div>
    <div class="box box3">
        <div>position</div>
    </div>
    <div class="box box4">
        <div class="cell">
            <div>table</div>
        </div>
    </div>
    <div class="box box5">
        <div>position+0</div>
    </div>

.box {
  width: 500px;
  height: 100px;
  background: lightblue;
  margin-bottom: 10px;
}
.box > div {
  width: 100px;
  height: 50px;
  line-height: 50px;
  text-align: center;
  background: pink;
}

.box1 {
  display: flex;
  justify-content: center;
  align-items: center;
}

.box2 {
  line-height: 100px;
  text-align: center;
}
.box2 > div {
  display: inline-block;
}

.box3 {
  position: relative;
}
.box3 > div {
  position: absolute;
  top: calc（50% - 25px）;
  left: calc(50% - 50px);
}

.box4 {
  display: table;
  vertical-align: center;
}
.box4 .cell {
  display: table-cell;
  background: lightblue;
  vertical-align: middle;
  text-align: center;
}
.box4 .cell > div {
  display: inline-block;
  background: pink;
  width: 100px;
  height: 50px;
}

.box5 {
  position: relative;
}
.box5 > div {
  position: absolute;
  margin: auto;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
}