1.v-if VS v-show:v-if适合运营条件不大可能改变；v-show适合频繁切换。
2.DOM中设置自适应高度：在monted生命周期中加上
this.$nextTick(() => {
let h =
window.innerHeight ||
document.documentElement.clientHeight ||
document.body.clientHeight;
this.$refs.List.style.height = "calc(" + h +"px - 3.9rem)";
});
