Transformer

Transformer<Input, Output>: (tree, file, next) => Promise<Output | undefined | void> | Promise<never> | Output | Error | undefined | void

Transformers handle syntax trees and files.

They are functions that are called each time a syntax tree and file are passed through the run phase. When an error occurs in them (either because it’s thrown, returned, rejected, or passed to next), the process stops.

The run phase is handled by trough, see its documentation for the exact semantics of these functions.

Note: you should likely ignore next: don’t accept it. it supports callback-style async work. But promises are likely easier to reason about.

Type Parameters

Type Parameter	Default type
Input extends ../../node_modules/@types/unist	../../node_modules/@types/unist
Output extends ../../node_modules/@types/unist	Input

Parameters

Parameter	Type
tree	Input
file	VFile
next	TransformCallback<Output>

Returns

Promise<Output | undefined | void> | Promise<never> | Output | Error | undefined | void

Defined in

node_modules/unified/lib/index.d.ts:1007