Checking if a field contains a string

I’m looking for an operator, which allows me to check, if the value of a field contains a certain string.

Something like:

db.users.findOne({$contains:{“username”:”son”}})
Is that possible?

node.js database

I’m looking for a database to pair with a node.js app. I’m assuming a json/nosql db would be preferable to a relational DB [I can do without any json/sql impedance mismatch]. I’m considering:
couchdb

MongoDB – paging

When using MongoDB, are there any special patterns for making e.g. a paged view?
say a blog that lists the 10 latest posts where you can navigate backwards to older posts.

Or do one solve it with an …