使用条件注释检测JS中的IE

// ----------------------------------------------------------
// A short snippet for detecting versions of IE in JavaScript
// without resorting to user-agent sniffing
// ----------------------------------------------------------
// If you're not in IE (or IE version is less than 5) then:
//     ie === undefined
// If you're in IE (>=5) then you can determine which version:
//     ie === 7; // IE7
// Thus, to detect IE:
//     if (ie) {}
// And to detect the version:
//     ie === 6 // IE6
//     ie > 7 // IE8, IE9 ...
//     ie < 9 // Anything less than IE9
// ----------------------------------------------------------

// UPDATE: Now using Live NodeList idea from @jdalton

var ie = (function(){

    var undef,
        v = 3,
        div = document.createElement('div'),
        all = div.getElementsByTagName('i');

    while (
        div.innerHTML = '<!--[if gt IE ' + (++v) + ']><i></i><![endif]-->',
        all[0]
    );

    return v > 4 ? v : undef;

}());

此函数将返回IE主版本号为整数，如果浏览器不是Internet Explorer，则未定义。像所有用户代理解决方案一样，这很容易受到用户代理欺骗(这是IE版本8以来的官方功能)。

function getIEVersion() {
    var match = navigator.userAgent.match(/(?:MSIE |Trident\/.*; rv:)(\d+)/);
    return match ? parseInt(match[1]) : undefined;
}

检测IE及其版本再容易不过了，你所需要的只是一点原生/香草Javascript:

var uA = navigator.userAgent;
var browser = null;
var ieVersion = null;

if (uA.indexOf('MSIE 6') >= 0) {
    browser = 'IE';
    ieVersion = 6;
}
if (uA.indexOf('MSIE 7') >= 0) {
    browser = 'IE';
    ieVersion = 7;
}
if (document.documentMode) { // as of IE8
    browser = 'IE';
    ieVersion = document.documentMode;
}

下面是一种用法:

if (browser == 'IE' && ieVersion <= 9) 
    document.documentElement.className += ' ie9-';

.

适用于所有IE版本，包括更高版本的低兼容性视图/模式，documentMode是IE专有的。

下面的代码依赖标识了所有情况下的IE版本(IE<=9, IE10, IE11和IE/Edge)

function detectIE() {
    var ua = window.navigator.userAgent;
    var msie = ua.indexOf('MSIE ');
    if (msie > 0) {
        // IE 10 or older => return version number
        return parseInt(ua.substring(msie + 5, ua.indexOf('.', msie)), 10);
    }
    var trident = ua.indexOf('Trident/');
    if (trident > 0) {
        // IE 11 => return version number
        var rv = ua.indexOf('rv:');
        return parseInt(ua.substring(rv + 3, ua.indexOf('.', rv)), 10);
    }
    var edge = ua.indexOf('Edge/');
    if (edge > 0) {
        // Edge (IE 12+) => return version number
        return parseInt(ua.substring(edge + 5, ua.indexOf('.', edge)), 10);
    }
    // other browser
    return false;
}

裁判:https://codepen.io/gapcode/pen/vEJNZN

使用条件注释。您正在尝试检测IE < 9的用户，条件注释将在这些浏览器中工作;在其他浏览器(IE >= 10和非IE)中，注释将被视为正常的HTML注释，这就是它们的本质。

示例HTML:

<!--[if lt IE 9]>
WE DON'T LIKE YOUR BROWSER
<![endif]-->

如果你需要，你也可以用脚本来完成:

var div = document.createElement("div");
div.innerHTML = "<!--[if lt IE 9]><i></i><![endif]-->";
var isIeLessThan9 = (div.getElementsByTagName("i").length == 1);
if (isIeLessThan9) {
    alert("WE DON'T LIKE YOUR BROWSER");
}

function getIEVersion(){
     if (/MSIE |Trident\//.test( navigator.userAgent )=== false) return -1;
    /**[IE <=9]*/
    var isIE9L = typeof ( window.attachEvent ) === 'function' && !( Object.prototype.toString.call( window.opera ) == '[object Opera]' ) ? true : false;
    var re;
    if(isIE9L){
        re = new RegExp( "MSIE ([0-9]{1,}[\.0-9]{0,})" );
        if(re.exec( navigator.userAgent ) !== null)
            return parseFloat( RegExp.$1 );
        return -1;
    }
    /**[/IE <=9]*/
    /** [IE >= 10]*/
    if(navigator.userAgent.indexOf( 'Trident/' ) > -1){
        re = new RegExp( "rv:([0-9]{1,}[\.0-9]{0,})" );
        if(re.exec( navigator.userAgent ) !== null)
            return parseFloat( RegExp.$1 );
        return -1;
    }
    /**[/IE >= 10]*/
    return -1;
};

点击这里==>

var ieVersion = getIEVersion();

if(ieVersion < 0){
    //Not IE
}
//A version of IE

了解关于浏览器导航器的更多信息 https://developer.mozilla.org/en-US/docs/Web/API/Window/navigator