vue mixin 屏幕滚动到底部监听

export const scrollEvent = {
    methods: {
        onScroll(){
            // 变量scrollTop是滚动条滚动时，距离顶部的距离
            var scrollTop =
                document.documentElement.scrollTop ||
                document.body.scrollTop;
            // 变量windowHeight是可视区的高度
            var windowHeight =
                document.documentElement.clientHeight ||
                document.body.clientHeight;
            // 变量scrollHeight是滚动条的总高度
            var scrollHeight =
                document.documentElement.scrollHeight ||
                document.body.scrollHeight;
            // 滚动条到底部的条件
            if (scrollTop + windowHeight == scrollHeight) {
                // 滚动到底部    调用页面方法
                this.onPageScroll && this.onPageScroll();
            }
        }
    },
    mounted() {
        window.addEventListener('scroll', this.onScroll)
    },
    destroyed() {
        window.removeEventListener('scroll', this.onScroll, false);
    },
}