Mongodb $in against a field of objects of array instead of objects of array

Question

arr=[{field1:,field2:

I want to use the $in operator against the field1 of arr. I

Answer 1

You need to extract the "location" fields from your input array and feed them to $in:

var locs = arr.map(function(x) { return x.location } );
db.collection.find({ "fieldx": { "$in": locs } })

---

For reference here I'm going to re-write your question for you:

I have a collection that contains documents like this:

{ "fieldx": "NY" }
{ "fieldx": "LA" }
{ "fieldx": "SF" }

What I have is an input array that is defined like this:

var arr = [
    { "name": "foo", "location": "NY"},
    { "name": "bar", "location": "LA"},
    { "name": "foobar", "location": "NZ"}
];

Now I want to write a query to find all the documents that match the "location" field in the array I have for input.

How do I do I do that?

I have tried:

db.collection.find({ "fieldx": { "$in": arr } })

But that does not match.