JS下拉菜单实现-CFANZ编程社区

1.HTML

<body>
    <ul id="nevigation">
        <li>
            <button class="dropbtn">菜单一</button>
            <ul class="list">
                <li class="item"><a href="#" target="_blank">项目一</a></li>
                <li class="item"><a href="#" target="_blank">项目二</a></li>
                <li class="item"><a href="#" target="_blank">项目三</a></li>
                <li class="item"><a href="#" target="_blank">项目四</a></li>
            </ul>
        </li>
        <li>
            <button class="dropbtn">菜单一</button>
            <ul class="list">
                <li class="item"><a href="#" target="_blank">项目一</a></li>
                <li class="item"><a href="#" target="_blank">项目二</a></li>
                <li class="item"><a href="#" target="_blank">项目三</a></li>
                <li class="item"><a href="#" target="_blank">项目四</a></li>
            </ul>
        </li>
        <li>
            <button class="dropbtn">菜单一</button>
            <ul class="list">
                <li class="item"><a href="#" target="_blank">项目一</a></li>
                <li class="item"><a href="#" target="_blank">项目二</a></li>
                <li class="item"><a href="#" target="_blank">项目三</a></li>
                <li class="item"><a href="#" target="_blank">项目四</a></li>
            </ul>
        </li>
        <li>
            <button class="dropbtn">菜单一</button>
            <ul class="list">
                <li class="item"><a href="#" target="_blank">项目一</a></li>
                <li class="item"><a href="#" target="_blank">项目二</a></li>
                <li class="item"><a href="#" target="_blank">项目三</a></li>
                <li class="item"><a href="#" target="_blank">项目四</a></li>
            </ul>
        </li>
    </ul>
</body>

2.CSS样式

    <style type="text/css">
        * {
            padding: 0px;
            margin: 0px;
            box-sizing: border-box;
        }

        a {
            text-decoration: none;
            color: #fff;
        }

        li {
            list-style: none;
        }

        #nevigation li {
            float: left;
            text-align: center;
            position: relative;
        }

        .dropbtn {
            background-color: #0098c2;
            color: white;
            border: none;
            height: 40px;
            width: 80px;
            margin-right: 5px;
        }

        .list {
            display: none;
            font-size: 12px;
            width: 80px;
            margin-right: 5px;
        }

        .item {
            width: 100%;
            height: 40px;
            border: 1px solid #fff;
            background-color: #255f9e;
        }

        .item a {
            display: block;
            width: 100%;
            height: 100%;
            line-height: 40px;
        }

        .item a:hover {
            background-color: #ffb100;
        }

        .change {
            display: block;
            font-size: 12px;
            width: 80px;
            margin-right: 5px;

        }
    </style>

<script>
    var btns = document.getElementsByClassName('dropbtn');

    /* var lists = document.getElementsByClassName('list');
    function myDropdown(i) {
        var btn = btns[i];
        var temp = lists[i];
        btn.onfocus = function () {
            temp.className = ' list change';
        }
        btn.onblur = function () {
            temp.className = s'list';
        }
    }
    myDropdown(1); */

    for (var i = 0; i < btns.length; i++) {
        btns[i].onmouseover = function () {
            for (var i = 0; i < btns.length; i++) {
                //  nextElementSibling 得到下一个兄弟元素节点 即ul
                btns[i].nextElementSibling.className = 'list';
            }
            this.nextElementSibling.className = 'list change';
        }
    }
</script>