Javascript 浏览器探测

1、根据浏览器的性能
 var is = {
 ff: window.globalStorage,
 ie: document.all && !window.opera,
 ie6: !window.XMLHttpRequest,
 ie7: document.all && window.XMLHttpRequest && !XDomainRequest && !window.opera,
 ie8: document.documentMode==8,
 opera: Boolean(window.opera),
 chrome: Boolean(window.chrome),
 safari: window.getComputedStyle && !window.globalStorage && !window.opera
}
2、通过解析navigator对象
如：var isFirefox=(navigator.userAgent.indexOf("Gecko")!==-1);
    var isMacWebKit=(nacigator.userAgent.indexOf("Macintosh")!==-1 && navigator.userAgent.indexOf("WebKit"));