js滚动加载到底部

<script>
//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;
};
//获取当前可是范围的高度
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);
};

window.onscroll = function () {
if (getScrollTop() + getClientHeight() == getScrollHeight()) {
alert("到达底部");
}
}
</script>