Code actions

When the graph is not enough, the Code box runs a script.

Seven languages are available, all of them run inside an embedded WebAssembly sandbox: no interpreter is required on your machine, and the script has no access to your file system.

Language	Engine
TypeScript	QuickJS (types stripped at compile time)
JavaScript	QuickJS
Python	Pyodide (CPython compiled to WebAssembly)
Lua	Lua 5.4 in WebAssembly
Ruby	CRuby in WebAssembly
R	WebR
C#	.NET in WebAssembly with Roslyn

The default language is TypeScript.

The common contract

Whatever the language, the box exposes the same thing:


Inputs	`value` (named input), `code` (string)
Outputs	`result`
Configuration	`language`, `code`, `timeout`, `packages`

input — the value received on the input port.
vars — the run variables.
The language’s standard output (console.log, print, puts, cat, Console.WriteLine) feeds the execution log.
The value returned leaves on the result port. An error or a timeout leaves on error.

The timeout

timeout, in seconds: 5 by default, 60 at most. A script that goes over is interrupted and execution leaves via the error port.

External packages

The packages field accepts a list of { name, version }. The exact versions serve as the cache key: dependencies are resolved on the first run, cached, then mounted offline on every subsequent run — CI included.

Language	Source
TypeScript / JavaScript	npm (the whole set is bundled)
Python	Pure-Python wheels from PyPI
Lua	LuaRocks (pure-Lua sources)
Ruby	Pure-Ruby gems
R	CRAN, via WebR’s WebAssembly repository
C#	None — the .NET standard library only

When not to write code

Many needs are already covered by boxes, which are more readable and faster:

Need	Box
Extract a value from a response	A link selector
Format a string	Transform template
Filter, sort, aggregate a list	Lists
Hash, encode, sign	Encoding
Check a structure	Schema validate

Keep the Code box for logic that really is specific.