Abstract: A system and method is disclosed for tracking representations of object properties in modified computational objects. A computational object of the subject technology may include an object property having a first value of a first property type. When the object property is set to a second value of a second property type, a new object map is generated for the computational object, the new object map mapping the object property to the second property type, and transition information in a base object map is updated to designate the new object map instead of a first object map. The first object map is then marked as invalid.

Abstract: A system and method is disclosed for sharing type information between object maps. When an object data structure is modified in a dynamic programming environment to change an initial number of object properties a child object map for the modified object data structure is generated based on a parent object map for the unmodified object data structure, and a descriptor array associated with the base object map is shared with the child object map. The descriptor array is dynamically altered according to the modified object data structure, and access to the descriptor array is limited from the parent object map in accordance with the initial number of object properties of the unmodified object data structure.