Question

I’m working on a NodeJS+Mongodb app.

I’ve just inserted one record into mongodb using the console client:

db.user.save({myId:11111, myDate: ISODate("2012-04-30T00:00:00.000Z")})

The thing is, when I’m in node.js, I need to know if “myDate” field is really a Date type, in order to perform a data range query, etc.

I tried the following.

1. on the mongo client console:

typeof db.user.myDate --> It returns "Object"
db.user.myDate instanceof Date --> It returns "false"

2. on my Nodejs code,

I’m trying to get the type calling this getTypeMembers function. (obj comming from a db query)

exports.getTypeMembers = function(obj) {
obj = JSON.parse(JSON.stringify(obj)

for(var _k in obj){
    if(Object.prototype.toString.call(obj[_k]) === '[object Array]' ) {
        obj[_k] = "Array";
    }
    else if(typeof(obj[_k])=="object"){
        obj[_k] = this.getTypeMembers(obj[_k]);
    }else{
        obj[_k] = typeof (obj[_k]);
    }
}
return obj;

};

What I get in this method is: "String", when I need "Date"

Is there any other way to get some kind of "Date" result?

Answer 1

I finally found my solution.

As @christkv said, once you call a JSON stringify, all original types are definitely lost.
So, thinking in this way, my method getTypeMembers works perfectly for me.

Notice that, obj parameter is coming from the DB, and also “_id” (mongodb identificator) is directly ommited in order to avoid problems when performs the recursive function:

exports.getTypeMembers = function(obj) {
    for(var _k in obj){
        if (_k =="_id") continue;
        if (Object.prototype.toString.call(obj[_k]) === "[object Number]"){
            obj[_k] = "Number";
        }else if (Object.prototype.toString.call(obj[_k]) === "[object String]"){
            obj[_k] = "String";
        }else if (Object.prototype.toString.call(obj[_k]) === "[object Date]"){
            obj[_k] = "Date";
        } else if(Object.prototype.toString.call(obj[_k]) === '[object Array]' ) {
            obj[_k] = "Array";
        } else if(typeof(obj[_k])=="object"){
            obj[_k] = this.getTypeMembers(obj[_k]);
        } else{
            obj[_k]  = (typeof obj[_k])[0].toUpperCase() + (typeof obj[_k]).slice(1);
        }
    }
    return obj;
};

In the Mongo console part, I only can get the type doing the following:

db.user.find({},{myDate:1}).forEach(function(f) { print (f.myDate instanceof Date) } );

But If I do,

typeof db.user.myDate --> It returns "Object"
db.user.myDate instanceof Date --> It returns "false"

I still don’t undertand why.