Doing it wrong (i.e., typical JavaScript developer skill level)

gistfile1.txt

function translate(key) {
    try {
        var value = null;
        value = eval('Translations.' + key);
        _(arguments).chain().tail().each(function (arg, i) {
            value = value.replace(new RegExp('\\{' + i + '\\}', 'g'), arg);
        });
        return value;
    }
    catch (e) {
        console.error('Error translating ' + key, e);
        return key;
    }
}