function testB () {    // body...var isOpera = !!window.opera ||!!window.opr|| navigator.userAgent.indexOf(‘ OPR/‘) >= 0;    // Opera 8.0+ (UA detection to detect Blink/v8-powered Opera)var isFirefox = typeof InstallTrigger !== ‘undefined‘;   // Firefox 1.0+var isSafari = Object.prototype.toString.call(window.HTMLElement).indexOf(‘Constructor‘) > 0;//var isSafari =/constructor/i.test(window.HTMLElement)    // At least Safari 3+: "[object HTMLElementConstructor]"    var isChrome = !!window.chrome && !isOpera;              // Chrome 1+var isIE = /*@cc_on!@*/false || !!document.documentMode;   // At least IE6    console.log("是否是ie："+  isIE);    console.log("是否是chrome："+  isChrome);    console.log("是否是Firefox："+  isFirefox);    console.log("是否是opera："+ isOpera);    console.log("是否是safari："+isSafari);    if(isIE){        var verIEtrue="";        ///        verIEtrue = (function(){    // for-loop saves characters over while    for( var v = 3,             // b just as good as a div with 2 fewer characters             el = document.createElement(‘b‘),             // el.all instead of el.getElementsByTagName(‘i‘)             // empty array as loop breaker (and exception-avoider) for non-IE and IE10+             all = el.all || [];         // i tag not well-formed since we know that IE5-IE9 won‘t mind         el.innerHTML = ‘<!--[if gt IE ‘ + (++v) + ‘]><i><![endif]-->‘,         all[0];       );    // instead of undefined, returns the documentMode for IE10+ compatibility    // non-IE will still get undefined as before    return v > 4 ? v : document.documentMode;}() );        ///        console.log("ie的版本号："+  verIEtrue);    }}testB ();