One embodiment of the present invention provides a system that uses map objects to access object properties for a program written in a dynamic object-oriented programming language, thereby facilitating property access for languages that allow additional properties to be defined for objects at runtime. During operation, the system receives an object of an object type. This object is associated with a memory region and a given map object (from a set of map objects associated with the given object type) that describes how properties of the object are mapped to fields in the memory region. When receiving a request to access a property of the object, the system determines whether the given map object includes a field mapping for the property. If so, the system accesses a field in the memory region associated with the property using the field mapping.