UnrealJS¶
Embeds the V8 JavaScript engine inside UE. Lets you script UE in JavaScript.
Repo: ncsoft/Unreal.js
What it is¶
A C++ plugin that:
- Bridges UE's reflection system to V8
- Lets you write Blueprints in JS (
.uobject.js) - Hot-reloads JS without restarting the editor
- Auto-generates TypeScript typings for UE APIs
What it isn't¶
- Not a WebGL / three.js renderer. UnrealJS has no DOM, no canvas. It can't render web content.
- Not the same as MCP. UnrealJS is for scripting UE in JS; MCP is for external LLMs driving UE.
Use cases¶
- Script UE without C++ recompiles
- Game scripting for designers familiar with JS / TS
- Editor automation scripts in JS instead of Python
When to prefer over Python¶
| Concern | Python | UnrealJS |
|---|---|---|
| Editor scripting | Built-in, mature | Add-on |
| Game scripting | Limited | Better |
| Typings | Minimal | Full TS generation |
| Hot reload | Editor only | Yes |
| Community size | Larger | Smaller |
Caveats¶
- Maintenance is community-driven; UE version compatibility lags
- Building V8 from source is involved; use prebuilt plugin if possible
- Performance is JS-engine-bound (~5–10× slower than C++)