CSS設置div高度自動全屏

對body和html都設置高度100%

html,body {
  height: 100%;
  width: 100%;
  margin: 0 0 0 0;
  padding: 0 0 0 0;
  position: relative;
}

然後再對div設置100%

#app {
  height: 100%;
  width: 100%;
  margin: 0 0 0 0;
  padding: 0 0 0 0;
  position: relative;
}