eq

<a class="s">1</a>
<a class="s">2</a>
<a class="s">3</a>
<a class="s">4</a>
<a class="s">5</a>
<a class="s">6</a>
<a class="s">7</a>

获取相同类名的值，从上到下的顺序，从0开始

<script>

alert($(".s").eq(5).html()); 
</script>