jq选择（互斥）同级元素

页面：

<div class="r user-span clearfix" id="usertype">

<a  class="l on left"      href="javascript:void(0)" data="1">1</a><a  class="l off" href="javascript:void(0)" data="2">2</a><a  class="l off"     href="javascript:void(0)" data="3">3</a>

$('#usertype a').click(function(){    $(this).removeClass('off').addClass('on').siblings().removeClass('on');    var usertype = $(this).attr('data');});