What is the difference between the properties “id” and “cid” on a model object in Backbone Js?

The “id” property on a model is automatically assigned based on the “id” set in the model’s attributes hash.

Ideally, this is the ID that you receive from the rest API for the resource that you are querying. On the other hand, “cid” is an ID temporarily assigned to each model and is useful until an actual ID is determined for the object. For example, a model pushed to a collection that has not yet been persisted can be addressed using “cid”, until it is saved in the database and an actual ID is generated for it.