注意：要用var，不能用let,否则ie11以下会报错
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title></head><body><script>function IEVersion() {var userAgent = navigator.userAgent; //取得浏览器的userAgent字符串 var isIE = userAgent.indexOf("compatible") > -1 && userAgent.indexOf("MSIE") > -1; //判断是否IE<11浏览器 var isEdge = userAgent.indexOf("Edge") > -1 && !isIE; //判断是否IE的Edge浏览器 var isIE11 = userAgent.indexOf('Trident') > -1 && userAgent.indexOf("rv:11.0") > -1;if(isIE) {var reIE = new RegExp("MSIE (\\d+\\.\\d+);");reIE.test(userAgent);var fIEVersion = parseFloat(RegExp["$1"]);if(fIEVersion == 7) {return 7;} else if(fIEVersion == 8) {return 8;} else if(fIEVersion == 9) {return 9;} else if(fIEVersion == 10) {return 10;} else {return 6;//IE版本<=7} } else if(isEdge) {return 'edge';//edge} else if(isIE11) {return 11; //IE11 }else{return -1;//不是ie浏览器}}var a = IEVersion();if(a==-1){console.log('不是ie')}else{console.log('是ie','ie版本为---',a)}</script></body></html>
