JavaScript语言代码

我想使用这段JavaScript，以便根据访问者的浏览器语言显示特定页面。默认值应该是英语，因此如果语言不是脚本中设置的5种语言之一，它应该自动选择英语。目前，它似乎没有这样做。有人能帮我修改这段代码吗

var langcodes = ["es", "ca", "en" ,"nl", "fr", "de"];
var langCode = navigator.language || navigator.systemLanguage;
var lang = langCode.toLowerCase();
lang = lang.substr(0,2);
var dest = window.location.href;
for (i = langcodes.length-1; i >= 0; i--) {
    if (lang == langcodes[i]) {
        dest = dest.substr(0,dest.lastIndexOf('.')) + '-' + lang.substr(0,2) +
            dest.substr(dest.lastIndexOf('.'));
        window.location.replace ?
            window.location.replace(dest) :
            window.location=dest;
    }
}

---

没有循环的快速旋转，如果/否则

var langCode = navigator.language || navigator.systemLanguage;
var lang = langCode.toLowerCase();
lang = lang.substr(0,2);

var langs = {
"es" : "xyz.com/es.html",
"ca": "xyz.com/ca.html",
"nl": "xyz.com/nl.html",
"en": "xyz.com/en.html"
}

if(typeof langs[lang] == 'undefined'){
window.location = "xyz.com/en.html";
}
else{
window.location = langs[lang];
}