NodeJS use custom language outside application

i want to define language in other file and outside project to use simply any language into file. for example i'm using language into application as :

user.find({email: email}, function (err, users) {
    var len = users.length;
    if (len == 0) {
        newuser.save(function (err) {
            callback({'response': "Sucessfully Registered","result":true});
        });
    } else {
        callback({'response': "Email already Registered","result":false});
    }
});

now i want to require other file as lanugage name and use it into application for example:

var language = require('lang');
callback({'response': language ["email_registered"],"result":false});

how to define this file as array and use it into application?