previousAttributesmodel.previousAttributes() Return a copy of the model's previous attributes. Useful for getting a diff between versions of a model, or getting back to a valid state after an error occurs.

findWherecollection.findWhere(attributes) Just like where, but directly returns only the first model in the collection that matches the passed attributes.

indexBy

listenToOnceobject.listenToOnce(other, event, callback) Just like listenTo, but causes the bound callback to fire only once before being removed.

"reset" (collection, options) â when the collection's entire contents have been reset.

"error" (model_or_collection, response, options) â when a model's or collection's request to the server has failed.

filter (select)

"all" â this special event fires for any triggered event, passing the event name as the first argument followed by all trigger arguments.

contains (includes)

some (any)