JS根据不同浏览器加载不同css或JS

<script>
            function getBrowser() {
                var ua = window.navigator.userAgent;
                var isIE = ua.indexOf("MSIE") != -1 || ua.indexOf("Trident") != -1;
                var isIEEdge = ua.indexOf("Edge") != -1;
                var isFirefox = ua.indexOf("Firefox") != -1;
                var isOpera = window.opr != undefined;
                var isChrome = ua.indexOf("Chrome") && window.chrome;
                var isSafari = ua.indexOf("Safari") != -1 && ua.indexOf("Version") != -1;
                if(isIE) {
                    return "IE";
                } else if(isIEEdge) {
                    return "Edge";
                } else if(isFirefox) {
                    return "Firefox";
                } else if(isOpera) {
                    return "Opera";
                } else if(isChrome) {
                    return "Chrome";
                } else if(isSafari) {
                    return "Safari";
                } else {
                    return "Unkown";
                }
            }
            var linkNode = document.createElement("link");
            linkNode.setAttribute("rel", "stylesheet");
            linkNode.setAttribute("type", "text/css");
            if(getBrowser() == "IE" || getBrowser() == "Edge") {
                linkNode.setAttribute("href", "css/_edge.css");
            } else if(getBrowser() == "Safari") {
                linkNode.setAttribute("href", "css/_safari.css");
            } else {
                linkNode.setAttribute("href", "css/_chromeFF.css");
            }
            document.head.appendChild(linkNode);
        </script>