后3句 执行起来会显示不是JQ对象 那为什么visible 是JQ对象？？
<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>
