# Type Alias: MapperHandler (/pixi-vn-ink/index/type-aliases/MapperHandler)



\> **MapperHandler** = (`list`, `step`) => `PixiVNJsonOperation` | `undefined`

Defined in: [src/handlers/interfaces/HashtagHandler.ts:53](https://github.com/DRincs-Productions/pixi-vn-ink/blob/5604a832025db23627dcf27e489490f9e7743d04/src/handlers/interfaces/HashtagHandler.ts#L53)

A mapper function that converts a specific Hashtag-Command token list into a
PixiVNJsonOperation (or `undefined` when the command only modifies the step without
producing an operation, e.g. `call` / `jump`).

Unlike [HashtagHandler](/pixi-vn-ink/index/type-aliases/HashtagHandler), a mapper is purely synchronous and is **selected** by its
validation rule rather than deciding for itself whether to handle the command.  The selection
logic in [HashtagCommands.convertOperation](/pixi-vn-ink/index/namespaces/HashtagCommands/functions/convertOperation) tests each mapper's
[HashtagHandlerOptions.validation](/pixi-vn-ink/index/interfaces/HashtagHandlerOptions#validation) against the full token list; only the first matching
mapper is called.

## Parameters [#parameters]

### list [#list]

`string`\[]

### step [#step]

`PixiVNJsonLabelStep`

## Returns [#returns]

`PixiVNJsonOperation` | `undefined`

The PixiVNJsonOperation to enqueue, or `undefined` if the command only produces
side-effects on `step` (such as setting `labelToOpen`).