滚动下拉到底部的事件触发

//获取滚动条当前的位置
    function getScrollTop() {
        var scrollTop = 0;
        if (document.documentElement && document.documentElement.scrollTop) {
            scrollTop = document.documentElement.scrollTop;
        } else if (document.body) {
            scrollTop = document.body.scrollTop;
        }
        return scrollTop;
    };
 
    //获取当前可视范围的高度
    function getClientHeight() {
        var clientHeight = 0;
        if (document.body.clientHeight && document.documentElement.clientHeight) {
            clientHeight = Math.min(document.body.clientHeight, document.documentElement.clientHeight);
        } else {
            clientHeight = Math.max(document.body.clientHeight, document.documentElement.clientHeight);
        }
        return clientHeight;
    };
 
    //获取文档完整的高度
    function getScrollHeight() {
        return Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);
    };
 
    //滚动事件触发
    window.onscroll = function () {
        if (getScrollTop() + getClientHeight() === getScrollHeight()) {
            console.log("已经到底了，下拉不刷新")
        }
    };