js如何判断浏览器为ie6.0内核

var userAgent = navigator.userAgent.toLowerCase();

var browserId = userAgent.match(/(firefox|chrome|safari|opera|msie)/)[1];

var browserVersion = (userAgent.match(new RegExp('.+(?:version)[\/: ]([\\d.]+)')) || userAgent.match(new RegExp('(?:'+browserId+')[\/: ]([\\d.]+)')) || [0,'0'])[1];

var isIe6 = (browserId + browserVersion == msie6.0);

ie6.0为true，否则为false