mongo query where two fields match code example

Example 1: mongodb find documents where two fields are equal

db.myCollection.find( { $where: "this.a1.a != this.a2.a" } )

Example 2: mongodb match multiple fields

$match:
{
	$and: [
    {'ExtraFields.value': {$in: ["A52A2A"]}}, 
    {'ExtraFields.fieldID': ObjectId("5535627631efa0843554b0ea")}
    ]
}

Example 3: mongodb find multiple fields

{ <field1>: <value>, <field2>: <value> ... }