D3.js Data Join and DOM Synchronization with Stable Key Functions

When implementing a reusable chart component in D3.js (v7), the data join lifecycle relies on a key function to maintain a stable mapping between data points and DOM elements. This ensures that specific elements are updated rather than recreated during dataset mutations.

A challenge arises when the underlying data array is modified, but the key function continues to return the same identifier for a modified object. There is uncertainty regarding whether the enter selection is bypassed for existing keys even if the internal properties of the data object have changed, and how this affects the timing of subsequent transitions.

• Does a stable key function prevent the enter selection from triggering when the data object is updated but the key remains identical?
• How does D3 handle attribute transitions when the initial state of a newly bound element is undefined or of a different type than the target value?