Mapper class API

@christiansmith/mapper-js exports the Mapper class as its default and the validate function by name.

import Mapper, { validate } from '@christiansmith/mapper-js'

Constructor

const mapper = new Mapper(
  { mappings },
  { initializers, transformers, plugins }
)

The first argument carries the mapping registry: an object whose mappings key maps $id strings to mapping documents, for $ref and $extend resolution. $extend resolves as each mapping registers, and resolution consumes the keyword: the registry stores the flattened mapping, which stands alone if serialized or re-registered. The second argument carries the three extension registries. Pass empty objects for anything unused.

map

const { valid, errors, ...result } = await mapper.map(mapping, input)

Applies a mapping document to an input document and resolves to the envelope: the output with valid and errors merged in. map is asynchronous because plugins are; a mapping with no plugins still returns a promise.

Mapping documents are ordered maps. Parse them with a parser that preserves key order (standard YAML and JSON parsers do).

const mapping = parse(await Deno.readTextFile('mapping.yaml'))

For descriptor grammar, start at Descriptor forms and the keyword catalog.

validate

const report = validate(mapping) // well-formedness
const report = mapper.validate(mapping) // adds reachability

Both return the report { valid, errors, warnings } synchronously and never throw. The named export checks the mapping document’s own form; the method also checks every referenced name against the instance’s registries. Hand either one a descriptor object with pairings under mapping:; unlike map, validate does not wrap a bare pairing map. Details, diagnostic anatomy, and the wrapped-form caution: Mapping validation.