SOURCE

<div class='box'>
  这里面得东西是啥
  <button class='btn'>aaa</button>
  <div class='mask'></div>
  <div class='control'>
    <button>编辑</button>
    <button>删除</button>
  </div>
</div>

.box {
  position: relative;
  width: 200px;
  height: 200px;
  border: 1px solid;
  
  cursor: pointer;
  .mask {
    position: absolute;
    top: 0;
    background: #000;
    width: 100%;
    height: 100%;
    
    opacity: 0;
    z-index: 100;
    
    transition: all 0.3 ease;
  }
  .control {
    position: absolute;
    z-index: 200;
    top: 0;
    left: 0;
    display: flex;
    align-items:center;
    justify-content: center;
    width: 100%;
    height: 100%;
    opacity: 0;
    transition: all .5s ease;
  }
  &:hover {
    .mask {
      opacity: 0.2;
    }
    .control {
      opacity: 1;
    }
  }
}