MongoDB find where key equals string from array - mongodb

Question

I am trying to find in a collection all of the documents that have the given key equal to one of the strings in an array.
Heres an example of the collection.
{
roomId = 'room1',
name = 'first'
},
{
roomId = 'room2',
name = 'second'
},
{
roomId = 'room3',
name = 'third'
}
And heres an example of the array to look through.
[ 'room2', 'room3' ]
What i thought would work is...
collection.find({ roomId : { $in : [ 'room2', 'room3' ]}}, function( e, r )
{
// r should return the second and third room
});
How can i achieve this?
One way this could be solve would be to do a for loop...
var roomIds = [ 'room2', 'room3' ];
for ( var i=0; i < roomIds.length; i++ )
{
collection.find({ id : roomIds[ i ]})
}
But this is not ideal....

Answer 1

What you posted should work - no looping required. The $in operator does the job:
> db.Room.insert({ "_id" : 1, name: 'first'});
> db.Room.insert({ "_id" : 2, name: 'second'});
> db.Room.insert({ "_id" : 3, name: 'third'});
> // test w/ int
> db.Room.find({ "_id" : { $in : [1, 2] }});
{ "_id" : 1, "name" : "first" }
{ "_id" : 2, "name" : "second" }
> // test w/ strings
> db.Room.find({ "name" : { $in : ['first', 'third'] }});
{ "_id" : 1, "name" : "first" }
{ "_id" : 3, "name" : "third" }
Isn't that what you expect?
Tested w/ MongoDB 2.1.1