javascript-actions

Mendix JavaScript Actions Skill

Guidance for creating, calling, and dropping JavaScript actions in Mendix projects with MDL. JavaScript actions hold custom client-side logic and are called from nanoflows (not microflows — those use Java actions).

When to Use This Skill

• Adding client-side behaviour (browser/native APIs, DOM, fetch, geolocation, …)
• Logic that must run on the device rather than the server
• Calling an existing JavaScript action from a nanoflow
• Wrapping a marketplace/native capability exposed as a JS action

For server-side custom code, use Java actions instead (see java-actions).

Overview

A JavaScript action is two things on disk:

1. The model unit (JavaScriptActions$JavaScriptAction).
2. A source file javascriptsource/<Module>/actions/<Name>.js containing an exported async function.

CREATE JAVASCRIPT ACTION writes both. The MDL body you provide becomes the function body (between the BEGIN USER CODE / END USER CODE markers), so it normally returns a Promise.

Syntax

CREATE [OR MODIFY] JAVASCRIPT ACTION Module.Name ( parameters )
    RETURNS type
    [EXPOSED AS 'caption' IN 'category']
    [PLATFORM Web | Native | Hybrid | All]   -- default Web
AS $$
    <javascript>
$$;

DROP JAVASCRIPT ACTION Module.Name;

Clause order is fixed: returns, then exposed as, then platform, then as.

• AS $$ ... $$ is mandatory. Omitting the body causes no viable alternative at input '...'. Use a stub: AS $$ return Promise.resolve(false); $$.
• PLATFORM defaults to Web. Use Native, Hybrid, or All to widen.
• OR MODIFY updates an existing action in place (UUID preserved); without it, a duplicate name is an error (use create or modify to overwrite).

Parameter types

Same type system as Java actions:

• Primitives: String, Integer, Long, Decimal, Boolean, DateTime
• Entity: Module.EntityName · List: List of Module.EntityName
• Enumeration: ENUM Module.EnumName
• Type parameter (generics): declare EntityType: ENTITY <pEntity>, then use the bare pEntity for instance parameters
• Append NOT NULL to mark a parameter required.