navigator.userAgent

navigator.userAgent 检测是浏览器模式当前的浏览器模式为IE8 文档模式为IE7时候userAgent 检测结果为MSIE 8.0

"Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729)"