JS判断当前浏览器方法

function getOs() {
var OsObject = "";
if (isIE = navigator.userAgent.indexOf("MSIE") != -1) {
return "MSIE";
}
if (isFirefox = navigator.userAgent.indexOf("Firefox") != -1) {
alert(Firefox);
$("#Mar").css("margin-top", "10");
//return "Firefox";
}
if (isChrome = navigator.userAgent.indexOf("Chrome") != -1) {
return "Chrome";
}
if (isSafari = navigator.userAgent.indexOf("Safari") != -1) {
return "Safari";
}
if (isOpera = navigator.userAgent.indexOf("Opera") != -1) {
return "Opera";
}
}