Assume there is an object:

const object = {

  'foo': {

    'bar': [1, 2, 3]

  }

}

I need to push 4 to object.foo.bar array.

Right now I'm doing it like this:

const initialState = Immutable.fromJS(object)

const newState = initialState.setIn(

  ['foo', 'bar', object.foo.bar.length],

  4

)

console.log(newState.toJS())

But I don't really like it, since I need to use object.foo.bar.length in the path. In my real example object is nested much deeper, and getting array's length looks very ugly. Is there another, more convenient way?