前端（各種demo）二：左側導航欄的折疊和打開（不使用js）基礎版和升級版

文章出處

1.給div設置定位。

　　復習一下——

　　css中position有五種屬性：

　　　　static:默認值，沒有定位

　　　　absolute:絕對定位，相對于父級元素進行定位

　　　　relative:相對定位

　　　　fixed:固定定位,相對于瀏覽器窗口進行定位

　　　　inherit:從父元素繼承定位信息　　

除了默認值static和inherit之外，添加其他三種都可以實現窗口自適應。

在做管控類的項目的時候總會遇到右側的導航欄的折疊和打開問題，不使用js實現，純粹的css實現，更準確的說應該是使用css3的checked實現的。

主要屬性是：

menu :checked + .menu-item-list {
        max-height: 500px;
    }

效果：

代碼：

<!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>
    * {
        padding: 0;
        margin: 0;
        box-sizing: border-box;
    }
    menu {
        width: 180px;
        max-height: 100%;
        overflow: auto;
        background-color: #15f5f5;
    }    
    menu .menu-item {
        position: relative;
    }
    menu .menu-item > input {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 46px;
        opacity: 0;
        cursor: pointer;
    }
    .menu-parent:hover{
        background-color: rgba(0, 0, 0, 0.06);
    }
    .menu-parent:visited{
        color: #fff;
        background-color: #5375f1;
    }
    menu span {
        display: block;
        padding: 5px 10px;
        font-size: 16px;
        line-height: 36px;
        cursor: pointer;
    }
    menu span:hover {
        background-color: rgba(0, 0, 0, 0.06);
    }
    menu span:active{
        color: #fff;
        background-color: #5375f1;
    }
    menu span.menu-child {
        font-size: 14px;
        text-indent: 20px;
    }
    menu .menu-item-list {
        max-height: 0;
        overflow: hidden;
        transition: all .3s ease;
    }
    menu :checked + .menu-item-list {
        max-height: 500px;
    }
    </style>
</head>
<body>
    <div class="box">
        <menu>
            <div class="menu-item">
                <span class="menu-parent">菜單1</span>
                <input type="checkbox" name="" value="">
                <div class="menu-item-list">
                    <span class="menu-child">子菜單1</span>
                    <span class="menu-child">子菜單2</span>
                    <span class="menu-child">子菜單3</span>
                    <span class="menu-child">子菜單4</span>
                </div>
            </div>
            <div class="menu-item">
                <span class="menu-parent">菜單2</span>
                <input type="checkbox" name="" value="">
                <div class="menu-item-list">
                    <span class="menu-child">子菜單1</span>
                    <span class="menu-child">子菜單2</span>
                    <span class="menu-child">子菜單3</span>
                    <span class="menu-child">子菜單4</span>
                </div>
            </div>
            <div class="menu-item">
                <span class="menu-parent">菜單3</span>
                <input type="checkbox" name="" value="">
                <div class="menu-item-list">
                    <span class="menu-child">子菜單1</span>
                    <span class="menu-child">子菜單2</span>
                    <span class="menu-child">子菜單3</span>
                    <span class="menu-child">子菜單4</span>
                </div>
            </div>
        </menu>
    </div>
</body>
</html>

升級版

例如要實現這樣的：左側的底部長度不會隨著下拉而拉高。

代碼:

<!DOCTYPE html>
<html>

    <head>
        <meta charset="UTF-8">
        <title></title>
        <style type="text/css">
            * {
                padding: 0;
                margin: 0;
                box-sizing: border-box;
            }
            html,body{
                width: 100%;
                height: 100%;
            }
            
            header {
                width: 100%;
                height: 50px;
                background: #1A2940;
                color: #fff;
            }
            .box{
                width: 180px;
                height: 100%;
                background-color: #6a8bbc;
            }
            
            menu {
        width: 180px;
        /*height: calc(height-50);*/
        /*max-height: 100%;*/
        overflow: auto;
        background-color: #6a8bbc;
        
    }    
    menu .menu-item {
        position: relative;
    }
    menu .menu-item > input {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 46px;
        opacity: 0;
        cursor: pointer;
    }
    menu .menu-parent:hover{
         background: #1A2940;
    }
    menu .menu-parent:active{
        color: #fff;
        background-color: #5375f1;
    }
    menu .menu-parent:visited{
        color: #fff;
        background-color: #5375f1;
    }
    menu span {
        display: block;
        padding: 5px 10px;
        font-size: 16px;
        line-height: 36px;
        cursor: pointer;
    }
    menu span:hover {
        background: #1A2940;
        color: #fff;
    }
    menu span:active{
        color: #fff;
        background-color: #5375f1;
    }
    menu span.menu-child {
        font-size: 14px;
        text-indent: 20px;
    }
    menu .menu-item-list {
        max-height: 0;
        overflow: hidden;
        transition: all .3s ease;
    }
    menu :checked + .menu-item-list {
        max-height: 500px;
    }
     .tdcolor { color:red }
        </style>
        <script type="text/javascript">
            var menu = document.getElementsByTagName('menu-parent');
            window.onload = function(){
                for(var i=0;i<menu.length;i++){
                    menu[i].onclick = function(){
                        menuOnclick(this);
                    }
                }
            }
            function menuOnclick(obj){
                for(var j=0;j<menu.length;j++){
                    if(menu[j]==obj){
                        menu[j].className = 'tdcolor';
                    }
                }
            }
        </script>
    </head>

    <body>
        <header>
            <img src="/" />aliyun
        </header>
        <div class="box">
            <menu>
                <div class="menu-item">
                    <span class="menu-parent active">概覽</span>
                </div>
                <div class="menu-item">
                    <span class="menu-parent">軟件服務</span>
                </div>
                <div class="menu-item">
                    <span class="menu-parent">菜單1</span>
                    <input type="checkbox" name="" value="">
                    <div class="menu-item-list">
                        <span class="menu-child">子菜單1</span>
                        <span class="menu-child">子菜單2</span>
                        <span class="menu-child">子菜單3</span>
                        <span class="menu-child">子菜單4</span>
                    </div>
                </div>
                <div class="menu-item">
                    <span class="menu-parent">菜單2</span>
                    <input type="checkbox" name="" value="">
                    <div class="menu-item-list">
                        <span class="menu-child">子菜單1</span>
                        <span class="menu-child">子菜單2</span>
                        <span class="menu-child">子菜單3</span>
                        <span class="menu-child">子菜單4</span>
                    </div>
                </div>
                <div class="menu-item">
                    <span class="menu-parent">菜單3</span>
                    <input type="checkbox" name="" value="">
                    <div class="menu-item-list">
                        <span class="menu-child">子菜單1</span>
                        <span class="menu-child">子菜單2</span>
                        <span class="menu-child">子菜單3</span>
                        <span class="menu-child">子菜單4</span>
                    </div>
                </div>
            </menu>
        </div>
    </body>

</html>