49.overflow：visible 和 auto

屏幕快照 2019-01-25 12.36.37.png

层级关系
.container {
.scroller-container {
.right-container {
}
}
}

.container {
 height: 300px;
 width: 80%;
 background: yellow;
 overflow-y:auto;/scroller
}
.right-container {
 position: absolute;
 right: 0;
 width: 20%;
 height: 100px;
 background-color: red;
}
.scroller-container {
 width: 100%;
 height: 800px;
 background: white;
 opacity: .5;
}

屏幕快照 2019-01-25 12.36.56.png

.container {
  height: 300px;
  width: 80%;
  background: yellow;
  overflow-y:visible;
}
.right-container {
  position: absolute;
  right: 0;
  width: 20%;
  height: 100px;
  background-color: red;
}
.scroller-container {
  width: 100%;
  height: 800px;
  background: white;
  opacity: .5;
}

1. 注意看滚动条的位置，二者滚动的区域不同
2. auto那种方式可以实现红色区域fixed的效果（悬浮窗)