jquery怎么判断是否ie浏览器

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)

    };