> Finally, functional languages tend to fight against large, mutually-linked, mutable data structures, yet the layout engine of a browser is all about that.

Is the DOM (and LayoutObject et al.) truly a case where imperative object-oriented programming shines? In pure FP operations like insertion, bidirectional traversal, and moving objects between parents can be cumbersome because there is no implicit identity for the objects.

Curious whether this is true, or is there a way to implement a DOM-like API with mostly immutable values?