OneJS

About OneJS – Unity Editor Tool & Plugin

Unity UI Toolkit Scripting with React and TypeScript

OneJS integrates JavaScript in Unity without relying on an embedded browser or webview. By connecting a purpose-built QuickJS engine directly to UI Toolkit, the system enables developers to author editor tools and runtime interfaces using familiar web development workflows. It eliminates domain reload delays during interface design through hot reloading in both Edit and Play modes.

Architecture and Component Features

The package pairs modern front-end build tools with Unity's native UI hierarchy to ensure responsive interface execution:

• React Reconciler: Employs a custom React 19 reconciler that converts JSX structures directly into native VisualElement instances.
• Bundling Pipeline: Leverages esbuild to bundle TypeScript, npm dependencies, CSS Modules, and Tailwind-style utility classes into a single build output.
• Native Engine Interop: Features zero-allocation C# interop alongside built-in support for vector drawing, GPU compute routines, and 2D particle simulations.
• Target Execution: Executes scripts via QuickJS on desktop and mobile platforms, while WebGL builds execute directly on the host browser JavaScript engine at native JIT speed.
• Workflow Extensibility: Integrates Model Context Protocol (MCP) support to interface with development agents and provides modular themes for rapid layout styling.

By bypassing webviews and mapping layout logic to VisualElements, the framework provides a structured approach for Unity React UI development across runtime game projects and custom editor extensions.

Use Cases

• Data-Intensive In-Game HUDs: Useful for managing complex menus, inventories, and HUD components that benefit from reactive state handling.
• Cross-Platform Interface Authoring: Fits projects requiring a unified layout codebase that renders natively across desktop, mobile, and browser targets.
• Player-Facing Modding Support: Can serve as an isolated scripting layer that allows end users to safely construct custom game interfaces using TypeScript and React.
• Custom Editor Tooling: Relevant to teams seeking fast interface iteration when creating proprietary inspection panels and internal editor dashboards.

FAQ

Does the asset require a web browser component to display interfaces?

No. The system renders directly to Unity VisualElements via a custom reconciler, eliminating the performance overhead and memory footprint of embedded browsers.

How does the build pipeline process web dependencies?

An external Node.js environment utilizes esbuild to compile TypeScript files, resolve npm modules, and process styling sheets into a unified script bundle readable by the engine.

Can the scripting runtime interact with custom C# scripts?

Yes. The architecture includes zero-allocation C# interop bindings that permit bi-directional data flow between native C# game systems and the JavaScript environment.

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