JS Object model: prototype chain, typeof, instanceof #95

Implement the JavaScript object model with prototype-based inheritance.

Scope#

Build the core object system that underpins all JavaScript values: property storage, prototype chain lookup, and type-related operators.

Object Representation#

• Property map: string keys → property descriptors
• Data properties: value, writable, enumerable, configurable
• Accessor properties: get/set functions, enumerable, configurable
• Internal slots: [[Prototype]], [[Extensible]]
• Computed property keys (string and symbol)

Prototype Chain#

• [[Get]]: walk prototype chain for property lookup
• [[Set]]: set own property (respecting writable, setter)
• [[HasProperty]]: check own + prototype chain
• [[Delete]]: delete own property (respecting configurable)
• Object.create() semantics: create object with given prototype
• Object.getPrototypeOf / Object.setPrototypeOf

Operators#

• typeof — return type string ("undefined", "object", "boolean", "number", "string", "function", "symbol")
• instanceof — walk prototype chain checking against constructor.prototype
• in operator — [[HasProperty]] check
• delete operator — [[Delete]] on property

Property Enumeration#

• for...in enumeration (own + inherited enumerable string properties)
• Own property enumeration order (integer indices first, then insertion order)

Acceptance Criteria#

• Object type with property map and prototype pointer
• Property descriptors (data and accessor)
• Prototype chain lookup for property access
• typeof returns correct strings for all types
• instanceof walks prototype chain correctly
• in operator works for own and inherited properties
• delete operator respects configurable flag
• Property enumeration in correct order
• Object.create with null prototype works
• Unit tests for prototype chain, property descriptors, operators

Phase 10 — JavaScript Engine (issue 6 of 15). Depends on: JS Garbage Collector.