Mongoose ODM

Model.update

Updates all documents matching conditions using the update clause. All update values are casted to their appropriate types before being sent.

var conditions = { name: 'bourne' }
  , update = { $inc: { visits: 1 }}
  , options = { multi: true };

Model.update(conditions, update, options, callback);

function callback (err, numAffected) {
  // numAffected is the number of updated documents
})

Keep in mind that the safe option specified in your schema is used by default when not specified here.

Note: for backwards compatibility, all top-level update keys that are not $atomic operation names are treated as $set operations. Example:

var query = { name: 'bourne' };
Model.update(query, { name: 'jason bourne' }, options, callback)

// is sent as

Model.update(query, { $set: { name: 'jason bourne' }}, options, callback)

This helps prevent accidentally overwriting all of your document(s) with { name: 'jason bourne' }.

Also note: although values are casted to their appropriate types when using update, the following are not applied:

defaults
setters
validators
middleware triggered on save

If you want those features, please use the following convention rather than update:

Model.findOne({ name: 'bourne' }, function (err, doc){
  doc.name = 'jason bourne';
  doc.visits.$inc();
  doc.save();
});