Loops is a visual coordination language for making program behavior explicit.
Loops is designed for event-driven and interactive systems, where objects communicate through messages and callbacks. In such systems, the intention behind the wiring is often hard to see.
Loops makes flows first-class.
A Loops diagram is not just documentation. It is executable and defines what happens because of what.
Loops diagrams resemble sequence diagrams.
See more examples of Loops diagrams
Run an interactive demo of Loops in the browser
Experimental / research
Loops is a working prototype used to explore explicit control flow, coordination, and actor-based behavior. APIs, semantics, and tooling may change.
- A visual coordination language
- Focused on behavior and control flow, not computation
- Designed to work with JavaScript, not replace it
- Suitable for interactive systems, UI logic, workflows, and simulations
- Not a general-purpose programming language
- Not a UI framework
- Not a replacement for JavaScript or TypeScript
Loops programs are defined as diagrams.
A typical Loops class has several Loops programs.
Diagrams are drawn using the DrakonHub editor and saved as structured data.
Each diagram describes:
- a flow of execution,
- message passing between objects,
- conditional paths,
- and asynchronous behavior.
The diagram is the program.
The Loops compiler:
- reads diagrams exported from DrakonHub,
- validates their structure,
- and compiles them into bytecode.
The bytecode is a compact, deterministic representation of the diagram semantics.
The Loops runtime:
- executes the compiled bytecode,
- manages control flow and scheduling,
- and delivers messages between objects.
Loops supports asynchronous execution and delayed results.
A loop (a Loops program):
- takes one input argument,
- may produce zero, one, or many results,
- and results may arrive later in time.
Loops coordinates objects by sending messages.
Objects may be:
- instances of JavaScript classes, or
- finite state machines.
Loops does not generate application logic.
Instead:
- the developer provides the object implementations,
- Loops calls object methods exactly as specified by the diagrams,
- and object methods may be synchronous or asynchronous.
In other words:
JavaScript does the work. Loops coordinates the work.
This repository includes an interactive animated browser demo.
Run an interactive demo of Loops in the browser
The demo exists for a reason:
Reading logs and playing a system are two different things.
The demo was used to validate that the Loops model works under real interaction and time-based behavior.
Loops may be interesting to developers who care about:
- explicit control flow,
- coordination in event-driven systems,
- actor-based design,
- and making program behavior visible.
The Unlicense