​x
 
<html>
<head>
<script type="text/javascript" src="/jquery/jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
  $("button").click(function(){
    $("p").text(function(n){
    return "这个 p 元素的 index 是：" + n;
    });
  });
});
</script>
</head>
<body>
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
<button class="btn1">改变所有 p 元素的文本内容</button>
</body>
</html>
​