I made a simple calendar using ul li. Then I first used css to add a background: black using the selector #div ul li; then, I used the className of js to add a style active to all li. Then the background priority is not as high as it originally was, so what should I do...

p ul li.active{ //do something }

javascript - Issues about the priority of styles added by className.-PHP Chinese Network Q&A

I made a simple calendar, made with ul li, and then I first used css to use the selector #p ul li to add a background: black; then, I used the className of js to add a background to all li The style is active, and the background priority is not as high as it originally was. So what should I do to raise the priority to the highest level? -- Semi-finished code. .

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }

        #main{
            width: 500px;
            height: 300px;
        }

        #main ul li{
            float: left;
            width: 80px;
            height: 80px;
            background-color: gray;
            list-style: none;
            margin: 20px;
        }

        #main p{
            width: 300px;
            height: 80px;
            border: 1px solid red;
            position: absolute;
            top:350px;
        }

        .active{
            background:red;
            color: #fff;
            cursor: pointer;
        }
    </style>

    <script>
        window.onload=function()
        {
            var op = document.getElementById('main');
            var oLi = op.getElementsByTagName('li');
            var ap = op.getElementsByTagName('p')[0];
            var month = ['a','b','c','d','e','f','g','h','i','j','k','l']

            for(var i=0;i<oLi.length;i++)
            {
                oLi[i].index=i;
                oLi[i].onmouseover=function()
                {
                    for(var i=0;i<oLi.length;i++)
                    {
                        oLi[i].className="";
                    }
                    this.className="active";
                    ap.innerHTML = (this.index+1)+month[this.index];
                }
            }
        }
    </script>
</head>
<body>
    <p id="main">
        <ul>
            <li>1</li>
            <li>2</li>
            <li>3</li>
            <li>4</li>
            <li>5</li>
            <li>6</li>
            <li>7</li>
            <li>8</li>
            <li>9</li>
            <li>10</li>
            <li>11</li>
            <li>12</li>
        </ul>
        <p></p>
    </p>
</body>
</html>