JavaScript判断浏览器类型

function ceshi() {

var browserName = navigator.userAgent.toLowerCase();
if (/msie/i.test(browserName) && !/opera/.test(browserName)) {
alert("IE");
return;
} else if (/firefox/i.test(browserName)) {
alert("Firefox");
return;
} else if (/chrome/i.test(browserName) && /webkit/i.test(browserName) && /mozilla/i.test(browserName)) {
alert("Chrome");
return;
} else if (/opera/i.test(browserName)) {
alert("Opera");
return;
} else if (/webkit/i.test(browserName) && !(/chrome/i.test(browserName) && /webkit/i.test(browserName) && /mozilla/i.test(browserName))) {
alert("Safari");
return;
} else {
alert("unKnow");
}

}