<h2>可见性筛选选择器</h2>

    <h3>:visible/:hidden</h3>

    <div class="left">

        <div class="div">

            <a>display</a>

            <p id="div1" style="display:none;">display</p>

        </div>

        <div class="div">

            <a>width</a>

            <a>height</a>

            <p id="div2" style="width:0;height:0">width/height</p>

        </div>

        <div class="div">

            <a>visibility</a>

            <a>opacity</a>

            <p id="div3" style="visibility:hidden;opacity:0">visibility </p>

        </div>

    </div>

    <p id="show"></p>

<script type="text/javascript">

function show (ele) {

if (ele instanceof jQuery) {

$("#show").html('元素的长度的 = ' + ele.length)

} else {

alert(ele+' 不是jQuery对象')

}

}

</script>

    <script type="text/javascript">

    //查找id = div1的DOM元素,是否可见

    show($("#div1:visible"));

    </script>

    <script type="text/javascript">

    //查找id = div2的DOM元素,是否可见

    show( $("#div2:visible") );

    </script>

    <script type="text/javascript">

    //查找id = div3的DOM元素,是否可见

    show( $('#div3:visible')  );

    </script>

    <script type="text/javascript">

    //查找id = div1的DOM元素,是否隐藏

    show( '#div1:hidden' );

    </script>

    <script type="text/javascript">

    //查找id = div2的DOM元素,是否隐藏

    show( "#div2:hidden" );

    </script>

    <script type="text/javascript">

    //查找id = div3的DOM元素,是否隐藏

    show( "#div3:hidden" );

    </script>