跪求大神：js如何检测是不是IE8

用navigator.userAgent找MSIE 8.0 但用IE仿真一直是MSIE 9.0

---

var browser=navigator.appName 
var b_version=navigator.appVersion 
var version=b_version.split(";"); 
var trim_Version=version[1].replace(/[ ]/g,""); 
if((browser=="Microsoft Internet Explorer" && trim_Version=="MSIE8.0")){
    alert("IE8");
}

---

function checkBrower() {
    var Sys = {};
    var ua = navigator.userAgent.toLowerCase();
    if (window.ActiveXObject) {
        Sys.ie = ua.match(/msie ([\d.]+)/)[1];
        //获取版本
        var ie_version = 6;
        if (Sys.ie.indexOf("7") > -1) {
            ie_version = 7;
        }
        if (Sys.ie.indexOf("8") > -1) {
            ie_version = 8;
        }
        if (Sys.ie.indexOf("9") > -1) {
            ie_version = 9;
        }
        if (Sys.ie.indexOf("10") > -1) {
            ie_version = 10;
        }
        if (Sys.ie.indexOf("11") > -1) {
            ie_version = 11;
        }
    }
    else if (ua.indexOf("firefox") > -1)
        Sys.firefox = ua.match(/firefox\/([\d.]+)/)[1];
    else if (ua.indexOf("chrome") > -1)
        Sys.chrome = ua.match(/chrome\/([\d.]+)/)[1];
    else if (window.opera)
        Sys.opera = ua.match(/opera.([\d.]+)/)[1];
    else if (window.openDatabase)
        Sys.safari = ua.match(/version\/([\d.]+)/)[1];
}

---

var isIE = function(ver){
    var b = document.createElement('b')
    b.innerHTML = '<!--[if IE ' + ver + ']><i></i><![endif]-->'
    return b.getElementsByTagName('i').length === 1
}
if(isIE(6)){
    // IE 6
    //alert("现在是IE6的浏览器！");
}
// ...
if(isIE(9)){
    // IE 9
    //alert("现在是IE9的浏览器！");
}

var ie  = isIE()
        
        document.write('ie6:' + isIE(6) + '<br>' + 'ie7:' + isIE(7) + '<br>' + 'ie8:' + isIE(8) + '<br>' + 'ie9:' + isIE(9) + '<br>'  + 'ie10:' + isIE(10) + '<br>' + 'ie11:' + isIE(11) + '<br>'+ 'ie:' + isIE())

---

if (navigator.appName === 'Microsoft Internet Explorer') { //判断是否是IE浏览器
    if (navigator.userAgent.match(/Trident/i) && navigator.userAgent.match(/MSIE 8.0/i)) { //判断浏览器内核是否为Trident内核IE8.0
        console.info('IE8');
    }
}