Synchronous instantiation pattern -- flat JSON to actual, circular data structure?

JSON comes in with many object descriptions

These objects hold string references to other objects in this flat structure

Currently, we instantiate all objects and just retain the string references to other objects

I want the instances to have actual, object references to the other instances

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Is there any simple pattern for iterating this initial JSON in a synchronous manner?

Currently, we're essentially using forEach and new Class with each description

Thanks