Provide Map.setIn()

What is the preferred way to set a nested value? I see that there is updateIn(), which kind of does what I want, but it has two problems:

• It doesn’t set new keys, it can only update already existing keys.
• It uses an extraneous function for updating. The value I want to set is independent from the original value (undefined), so I don’t need any function to determine the new value.

How would you add a new key ‘d’ with a single line? What’s the API for this?

var mutableObject = {
  test: { test2: { a:1, b:2, c:3 } }
};
var immutableObject = Immutable.fromJS(mutableObject);

// desired mutation:
// {
//   test: { test2: { a:1, b:2, c:3, d:4 } }
// );

// with mutable objects it's very simple:
mutableObject.test.test2.d = 4;

// with immutable objects it doesn't seem to be possible:
immutableObject = immutableObject.setIn(['test', 'test2', 'd'], 4); // TypeError

[leebyron]

Nope, after this diff landed, you can now write:

oldMap.setIn([‘test1’, ‘test2’, ‘d’], 4);

[evenstensberg]

@leebyron do we still need to use newMap = oldMap.updateIn(['test1', 'test2'], x => x.set('d', 4)); to add a prop to the object or how do you do this in a “cleaner” way?