Why are Iso Subspaces required for C++ fields?

Iso Subspaces provide a dedicated memory region for specific object types, allowing the JavaScriptCore garbage collector to safely manage objects that contain native C++ data.

How do I define a read-only property in this framework?

You use the HashTableValue array with PropertyAttribute::ReadOnly and PropertyAttribute::CustomAccessor, then define a corresponding JSC_DEFINE_CUSTOM_GETTER.

What is the 3-class structure for JSC implementations?

For publicly accessible constructors, you create an Object class (for instances), a Prototype class (for shared methods), and a Constructor class (for the internal function that creates instances).

Where should class structures be cached in Bun?

Structures should be cached in ZigGlobalObject.h using JSC::LazyClassStructure and initialized within ZigGlobalObject.cpp to ensure efficient reuse across the runtime.

JSC C++ Class Implementation

Name: JSC C++ Class Implementation
Author: oven-sh

byoven-sh

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86,659

API Development

Streamlines the creation of high-performance JavaScript classes in C++ using the JavaScriptCore engine.

About

This skill provides standardized implementation patterns and boilerplate for building JavaScript classes in C++ within the Bun runtime environment. It guides developers through the complex process of defining the three-tier class architecture—Object, Prototype, and Constructor—while ensuring memory safety through Iso Subspaces. By following these established patterns for property definitions, getter/setter logic, and structure caching, developers can efficiently create robust native bindings that expose C++ functionality to the JavaScript layer with optimal performance.

Key Features

86,659 GitHub stars
LazyClassStructure caching for efficient global object integration
Iso Subspace configuration for memory safety and garbage collection
Declarative property, method, and custom accessor definitions
Native interoperability patterns for exposing C++ to Zig
Standardized 3-tier class architecture (Object, Prototype, Constructor)

Use Cases

Developing new native Web APIs or modules for the Bun runtime
Implementing complex native objects that require custom memory management in JSC
Optimizing performance-critical JavaScript classes by migrating logic to C++

About

Key Features

86,659 GitHub stars
LazyClassStructure caching for efficient global object integration
Iso Subspace configuration for memory safety and garbage collection
Declarative property, method, and custom accessor definitions
Native interoperability patterns for exposing C++ to Zig
Standardized 3-tier class architecture (Object, Prototype, Constructor)

Use Cases

Developing new native Web APIs or modules for the Bun runtime
Implementing complex native objects that require custom memory management in JSC
Optimizing performance-critical JavaScript classes by migrating logic to C++