原理就是监听页面滚动事件，分析clientHeight、scrollTop、scrollHeight三者的属性关系。
方法：
window.addEventListener('scroll', function() {
const clientHeight = document.documentElement.clientHeight;
const scrollTop = document.documentElement.scrollTop;
const scrollHeight = document.documentElement.scrollHeight;
if (clientHeight + scrollTop >= scrollHeight) {
// 检测到滚动至页面底部，进行后续操作
// ...
}
}, false);
例子：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.content {
height: 200px;
}
.one {
background-color: red;
}
.two {
background-color: blue;
}
.there {
background-color: black;
}
.four {
background-color: cadetblue;
}
</style>
</head>
<body>
<div class="main">
<div class="content one"></div>
<div class="content two"></div>
<div class="content there"></div>
<div class="content four"></div>
</div>
</body>
<script>
window.addEventListener('scroll', function() {
const clientHeight = document.documentElement.clientHeight;
const scrollTop = document.documentElement.scrollTop;
const scrollHeight = document.documentElement.scrollHeight;
if (clientHeight + scrollTop >= scrollHeight) {
const eleOne = document.createElement('div');
eleOne.setAttribute('class', 'content one');
const eleTwo = document.createElement('div');
eleTwo.setAttribute('class', 'content two');
const eleThere = document.createElement('div');
eleThere.setAttribute('class', 'content there');
const eleFour = document.createElement('div');
eleFour.setAttribute('class', 'content four');
const fragment = document.createDocumentFragment();
fragment.append(eleOne, eleTwo, eleThere, eleFour);
document.querySelector('.main').appendChild(fragment);
}
}, false);
</script>
</html>
