How to check if object is Immutable?

Immutable object can be an instance of:

• Immutable.List
• Immutable.Map
• Immutable.OrderedMap
• Immutable.Set
• Immutable.OrderedSet
• Immutable.Stack

There is an open ticket to improve the API which is on the roadmap for 4.0. Until this is implemented, I suggest you use Immutable.Iterable.isIterable() (docs).

Using instanceof is not reliable (e. g. returns false when different modules use different copies of Immutable.js)