Documentation
2. Authoring Language & Syntax
- Created
- Jun 5, 2026
- Updated
- Jun 5, 2026
Both custom indicators and strategies use one authoring engine, so the accepted language is identical. This page describes what you can write and what is rejected.
TypeScript and JavaScript
You can write TypeScript or JavaScript. Types are stripped, not type-checked — annotations are allowed and erased at compile time, so they document intent but do not validate it. ESM import/export syntax is recognized, and export default is the expected way to export your module.
Module shape
export default {
name: "My Study", // optional label
init(ctx) { /* … */ }, // optional, runs once
next(ctx) { /* … */ } // runs once per bar
};A bare top-level return { … } is also accepted for back-compat.
Strict by default
The engine runs in strict mode and rejects known footguns up front with a clear error, rather than compiling and misbehaving silently. The following are not allowed:
| Rejected | Why |
|---|---|
async init/next | The per-bar engine is synchronous; async functions never settle in time. |
Returning a Promise from next | A result would be silently dropped. |
import of values (and dynamic import()) | Authored modules must be self-contained. (import type … is fine — it is erased.) |
TypeScript namespace / module blocks | They compile but are erased, then throw at runtime. |
| Decorators | Not supported. |
Sandboxing
Authored code cannot reach the browser environment. A long list of globals — including window, document, fetch, XMLHttpRequest, WebSocket, localStorage, process, require, setTimeout, setInterval, and Worker — is shadowed (passed in as undefined), so your code is a pure, self-contained computation. Strategies additionally run inside a worker that can be hard-terminated.
Errors
- A compile-time problem (syntax error, banned construct, or bad module shape) is reported before the run, with a message and — where possible — a line number.
- A runtime error inside
next()is contained: for an indicator it nulls just that bar and continues; it never aborts the whole series.
Next steps
Put the language to work in a custom indicator.