tree.a= {...tree.a }

tree.a= { e:1 }

Here is my implementation of the[observable state tree](https://github.com/mfbx9da4/observable-state-tree/blob/main/observableStateTree/observableStateTree.ts#L13). I couldn't quite get the above API but I came[pretty close by using proxies](https://github.com/mfbx9da4/observable-state-tree/blob/main/pages/dotNotationExample.tsx). See the[react example here](https://github.com/mfbx9da4/observable-state-tree/blob/main/pages/reactExample.tsx).

Here is my implementation of the[observable state tree](https://github.com/mfbx9da4/observable-state-tree/blob/main/observableStateTree/observableStateTree.ts#L13). I couldn't quite get the above API but I came[pretty close by using proxies](https://github.com/mfbx9da4/observable-state-tree/blob/main/pages/dotNotationExample.tsx). See the[react example here](https://github.com/mfbx9da4/observable-state-tree/blob/main/pages/reactExample.tsx). See the[rudimentary unit tests here](https://github.com/mfbx9da4/observable-state-tree/blob/main/pages/unitTests.ts).