5.7

背景固定
background-attachment: fixed;
绝对定位水平居中
position: absolute;
left: 50%;
transform: translateX(-50%);
目标后添加元素，可以添加各种样式
::after {
    content: '';// 内容，必须
}
<script>

    let $ = {
        get(url, success) {
            this.ajax({
                url,
                success
            })
        },
        ajax({ type, url, async, success }) {
            let ajax = new XMLHttpRequest()
            ajax.open(type || 'GET', url, async || true)
            ajax.send()
            ajax.onreadystatechange = () => {
                if (ajax.readyState === 4) {
                    if (ajax.status === 200) {
                        success(JSON.parse(ajax.response))
                    }
                }
            }
        }
    }

    $.get('/5月/5.7.json', function (data) {
        console.log('打印', data);
    })

</script>