JS获取滚动条到底部得距离

// 监听滚动 FirstPage 是父组件传过来的值 判断调用哪个的addEvent() {window.addEventListener('scroll',this.type == 'FirstPage' ? this.firstPageScrollEvent : this.scrollDomScrollEvent);},// 滚动出首页则展示firstPageScrollEvent() {const height = document.getElementsByTagName('html')[0].clientHeight;const scrollTop =document.getElementsByTagName('html')[0].scrollTop ||document.getElementsByTagName('body')[0].scrollTop; let scrollHeight = document.documentElement.scrollHeight || document.body.scrollHeight// 变量 windowHeight 是可视区的高度let windowHeight = document.documentElement.clientHeight || document.body.clientHeight// let scrollTop1 = document.documentElement.scrollTop || document.body.scrollTop// 滚动条到底部得距离 = 滚动条的总高度 - 可视区的高度 - 当前页面的滚动条纵坐标位置var scrollBottom = scrollHeight - windowHeight - scrollTopconsole.log(scrollBottom,'scrollBottom')this.isShow = scrollTop > height; //出来if(scrollBottom==0){this.isShow=false //隐藏}},// 滚动出某个节点scrollDomScrollEvent() {const dom = document.getElementsByClassName(this.domClassName)[0];const height = dom.clientHeight;const lockScrollTop = dom.offsetTop - 100;const scrollTop =document.getElementsByTagName('html')[0].scrollTop ||document.getElementsByTagName('body')[0].scrollTop;this.isShow = scrollTop > height + lockScrollTop;},