Javascript 动态地将升序ID附加到元素

我试过：

每个功能：

描述：迭代jQuery对象，为每个匹配的元素执行一个函数

<p class="abc">Lorem ipsum</p>
<p class="xyz">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer ac lectus ac sapien cursus ullamcorper. Proin facilisis accumsan ante, at iaculis magna aliquam consectetur.</p>

<p class="abc">Lorem ipsum</p>
<p class="xyz">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer ac lectus ac sapien cursus ullamcorper. Proin facilisis accumsan ante, at iaculis magna aliquam consectetur.</p>

<p class="abc">Lorem ipsum</p>
<p class="xyz">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer ac lectus ac sapien cursus ullamcorper. Proin facilisis accumsan ante, at iaculis magna aliquam consectetur.</p>

 <p class="xyz" id="p1"></p>
 <p class="xyz" id="p2"></p>
 <p class="xyz" id="p3"></p>

$js = jQuery.noConflict();
$js(document).ready(function(){ 
    var count = $js('.xyz').length;  //here count = 3
});

$js(document).ready(function(){        
    $js('.xyz').each(function(index)
    {
        $js(this).attr('id', 'p' + (index + 1))
    });
});