Ajax请求实例,与懒加载技术

<!DOCTYPE html>
<html lang="en">
<head>
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    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <ul>
    </ul>
    <img width="100%" data-src="https://img.php.cn/upload/article/000/000/003/60c034e9d3595631.jpg" alt="" />
    <img width="100%" data-src="https://www.php.cn/static/images/index_yunv.jpg" alt="" />
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    <img width="100%" data-src="https://img.php.cn/upload/course/000/000/001/5d1c6dfc9eb09885.jpg" alt="" />
    <script>
// ### 2.1 xhr 请求步骤
// 1. 创建 xhr 对象: `const xhr = new XMLHttpRequest()`
// 2. 配置 xhr 参数: `xhr.open(type, url)`
// 3. 处理 xhr 响应: `xhr.onload = (...) => {...}`
// 4. 发送 xhr 请求: `xhr.send(...)`
// 问：Ajax get,post请求的区别
//      答：get请求参数会出现在地址栏，一般用户读取数据
//      答：post请求的参数会隐藏在请求头中，地址栏不会发生任何变化，相对较安全，一般用于提交数据
getData();
function getData(){
    const xhr = new XMLHttpRequest();
    let url = "https://api.apiopen.top/videoCategory";
    xhr.open('GET',url);
    xhr.responseType = 'json';
    xhr.onload = function (e){
        // console.log(e.currentTarget.response.result.itemList);
        const ul = document.querySelector('ul');
        for(let i = 0;i<e.currentTarget.response.result.itemList.length;i++){
            const li = document.createElement('li');
            li.textContent = e.currentTarget.response.result.itemList[i].data.description;
            li.style.height = '3rem';
            ul.append(li);
        }
    }
    xhr.onerror = function (){console.log('请求错误！')};
    xhr.send(null);
}
//onscroll 实现懒加载
    let img = document.images;
    window.onscroll = function(){
        [...img].forEach(img =>{
            if(img.getBoundingClientRect().top < window.innerHeight){
                img.src = img.dataset.src;
            }
        })
    }
</script>
</body>
</html>

Correcting teacher：

PHPz

Correction status：qualified

Teacher's comments：

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Ajax请求实例,与懒加载技术