浏览器判断

useragent.js

/*
* @link :http://browserhacks.com/
* IE篇
*/
var ie6=!-[1,]&&!window.XMLHttpRequest; //IE6为true,其他都为false
var isIE = !!window.ActiveXObject; //ie6-10都为true, ie11为false
/*返回IE6-9的版本号*/
var _IE = (function(){
    var 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 : false ;
}());

/*
* @link :http://browserhacks.com/
* chrome篇
*/
var isChromium = !!window.chrome;  //Chromium为true.
var isChrome = !!window.chrome && !!window.chrome.webstore; //chrome为true.
/*
* @link :http://browserhacks.com/
* Firefox篇
*/
var isFF = !!window.sidebar;