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

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .focus{
            color: #fff;
            background-color: red;
        }
        .fs{
            font-size: 80px;
        }
    </style>
</head>

<body>
    <div>
        <span class="focus">首页</span>
        <span>新闻</span>
        <span>图片</span>
        <span>热点</span>
    </div>
    <div id="tip">你好</div>
</body>
</html>
<script>
    var spans = document.getElementsByTagName('span');
    spans[0].setAttribute('title','这是一个首页')
    spans[1].setAttribute('title',spans[0].getAttribute('title'))
    spans[0].removeAttribute('title')

    var tip = document.getElementById('tip');
    tip.className = 'focus fs'
    tip.style.color = 'yellow'
    tip.style.fontSize = '15px'


</script>