advance-task12/ajax/ajax.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0 2px;
            box-sizing: border-box;
        }

        #ct li,
        #load-more {
            display: block;
            line-height: 30px;
            margin: 10px auto;
            padding: 5px 10px;
        }

        #ct li {
            list-style: none;
            border: 1px solid #ccc;
        }

        #ct li:hover {
            background: #ccc;
            color: white;
        }

        #load-more {
            color: red;
            text-decoration: none;
            border: 1px solid red;
            border-radius: 5px;
            width: 100px;
            text-align: center;
        }
    </style>
</head>

<body>
    <ul id="ct">
        <li>内容1</li>
        <li>内容2</li>
    </ul>
    <a href="#" id="load-more" class="btn">
        加载更多
    </a>
    
    <script>
        var ct = document.querySelector('#ct')
        var btn = document.querySelector('#load-more')
        var pageIndex = 3;

        var isDataArrive = true

        btn.addEventListener('click', function (e) {
            //取消a链接默认跳转到页面顶部的事件，直接将a标签內href的值改为javascript:void(0)也可，即href值为undefined
            e.preventDefault()

            if (!isDataArrive) {
                return
            }

            var xhr = new XMLHttpRequest()
            xhr.onreadystatechange = function () {
                if (xhr.readyState === 4) {
                    if (xhr.status === 200 || xhr.status === 304) {
                        var results = JSON.parse(xhr.responseText)
                        console.log(results);
                        var fragment = document.createDocumentFragment()
                        for (var i = 0; i < results.length; i++) {
                            var node = document.createElement('li')
                            node.innerText = results[i]
                            fragment.appendChild(node)
                        }
                        ct.appendChild(fragment)
                        pageIndex = pageIndex + 5
                    } else {
                        alert('出错了')
                    }
                    isDataArrive = true
                }
            }

           //远程可看 // xhr.open('get', 'https://www.mydolby.cn:9443/loadMore?index=' + pageIndex + '&length=5', true)
            
           //本地模拟
            xhr.open('get', 'http://localhost:8080/loadMore?index=' + pageIndex + '&length=5', true)
            
            xhr.send()
            isDataArrive = false
        })

    </script>
</body>

</html>