​x
 
<html>
<head>
<script type="text/javascript" src="/jquery/jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
  $(".btn1").click(function(){
    $("<b>Hello World!</b>").prependTo("p");
  });
});
</script>
</head>
<body>
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
<button class="btn1">在每个 p 元素的开头插入文本</button>
</body>
</html>
​