How to update a single field in a MongoDB collection for all documents matching a specific criteria

MongoDB update all matching.js

// FROM: http://www.mongodb.org/display/DOCS/Updating#Updating-update%28%29
// 
// db.collection.update( criteria, objNew, upsert, multi )
//   criteria - query which selects the record to update;
//   objNew - updated object or $ operators (e.g., $inc) which manipulate the object
//   upsert - if this should be an "upsert"; that is, if the record does not exist, insert it
//   multi - if all documents matching criteria should be updated
//
// SQL VERSION: 
// UPDATE myTable SET dateField = '2011-01-01' WHERE condField = 'condValue'


db.myCollection.update({condField: 'condValue'}, { $set: { dateField: new Date(2011, 0, 1)}}, false, true);