mongodb « Array « Javascript Data Type Q&A

1. MongoDB: Get count of Array    stackoverflow.com

Given these documents:

db.orders.insert( {OrderId:1, OrderItems: [{OrderItemId:1, Qty:1}, {OrderItemId:2, Qty:1} ]} );
db.orders.insert( {OrderId:2, OrderItems: [{OrderItemId:1, Qty:1}, {OrderItemId:2, Qty:2} ]} );

2. This looks like a job for MapReduce...but I just can't figure it out    stackoverflow.com

I've been battling with this for about 2 days now, and any help would be tremendously appreciated. I currently have a very large MongoDB collection(over 100M documents) in the following format:

[_id]
[date]
[score]
[meta1]
[text1]
[text2]
[text3]
[text4]
[meta2]

3. How to tell if an array of values all present in an array in a mongodb collection?    stackoverflow.com

I have some code that looks like this (all within the mongodb interpreter):

var needed_skills = ['mongodb','javascript','c++','php']

db.applicants.save( { name:'joe', skills:['c++','ruby','css'] } );
db.applicants.save( { name:'peter', skills:['mongodb','javascript','c++','php','html'] } );

4. Bulk insert from Array in mongodb JavaScript console    stackoverflow.com

I'm trying to make a bulk insert from the MongoDB console of an array into a collection. I'd like to do something similar to this.

obj1 = {_id:ObjectId(),blabla:1}; ...

5. Why doesn’t Array.some work in Mongo’s $where clause?    stackoverflow.com

I am using MongoDB 1.8.1. I want to emulate Mongo’s $elemMatch query inside a $where clause, using the standard some method on JavaScript arrays. However, the query never matches anything, even ...

6. Rejoining Split MapReduce Arrays in Mongo    stackoverflow.com

I'm just learning mapReduce. I have the following map reduce function being called on a collection of users.

function () {

    m = function () {
   ...

7. MongoDB: Function to Consolidate Arrays    stackoverflow.com

I have a large dataset with documents that sometimes cross-reference each other, sometimes do not. Before I can mapreduce based on those cross references, I have to set the array of ...