javascript如何判断浏览器是否为ie？

function detectIE() {
var ua = window.navigator.userAgent;
// Test values; Uncomment to check result …
// IE 10
// ua = 'Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)';
// IE 11
// ua = 'Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv:11.0) like Gecko';
// Edge 12 (Spartan)
/* ua = 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, 
like Gecko) 
Chrome/39.0.2171.71 Safari/537.36 Edge/12.0';*/
// Edge 13
/*ua = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, 
like Gecko) 
Chrome/46.0.2486.0 Safari/537.36 Edge/13.10586';*/
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;
}

这个方法是用来检测浏览器的版本，如果是非IE或者Edge的浏览器会返回false，如果是IE会返回对应的版本号。