jquery $.browser来判断浏览器实例

var userAgent = navigator.userAgent.toLowerCase();
// Figure out what browser is being used
jQuery.browser = {
version: (userAgent.match( /.+(?:rv|it|ra|ie)[/: ]([d.]+)/ ) || [])[1],
safari: /webkit/.test( userAgent ),
opera: /opera/.test( userAgent ),
msie: /msie/.test( userAgent ) && !/opera/.test( userAgent ),
mozilla: /mozilla/.test( userAgent ) && !/(compatible|webkit)/.test( userAgent )
};

$(function() {
if($.browser.msie) {
alert("this is msie");
}
else if($.browser.safari)
{
alert("this is safari!");
}
else if($.browser.mozilla)
{
alert("this is mozilla!");
}
else if($.browser.opera) {
alert("this is opera");
}
else {
alert("i don't konw!");
}

$.browser.msie&&($.browser.version == "6.0")&&!$.support.style