hidden class (Map/Shape)

RU: hidden class (Map/Shape)

An internal V8 structure (called Map in V8 source, Shape in SpiderMonkey) that describes an object's property layout — which named properties exist and at which memory offsets. Objects sharing the same hidden class allow V8 to resolve property accesses to a fixed offset without a hashtable lookup. Adding properties in a different order or deleting properties breaks the shared class and can degrade to dictionary mode.