【replaceall】
<html>
<head>
<script type="text/javascript" src='http://code.jquery.com/jquery-1.5.2.js'></script>
<script type="text/javascript">
$(document).ready(function(){
$("<b>Paragraph. </b>").replaceAll("span");
});
</script>
</head>
<body>
<span>Span Text</span>
</body>
</html>
