Skip to main content
Version: v0.1.13

Accept JSON and XML without writing the code twice

Both codecs produce the same model, so the format belongs at the edge of your program and nowhere else. Sniff it once, and everything downstream is format-blind:

import { parseResource, parseResourceXml, readSafety } from "@cosyte/fhir";
import type { ReadResult } from "@cosyte/fhir";

const read = (payload: string): ReadResult =>
  payload.trimStart().startsWith("<") ? parseResourceXml(payload) : parseResource(payload);

const fromJson = read('{"resourceType":"Observation","status":"final"}');
const fromXml = read('<Observation xmlns="http://hl7.org/fhir"><status value="final"/></Observation>');

readSafety(fromJson.resource).status; // => "final"
readSafety(fromXml.resource).status; // => "final"

Both readers hand back diagnostics on the same channel, issues on the read result, so one logging path covers both.

Check that two reads agree​

nodesEquivalent compares a model read from one format with a model read from the other, so a test or a migration can confirm that the JSON and the XML of a resource say the same thing:

import { nodesEquivalent, parseResource, parseResourceXml } from "@cosyte/fhir";

const fromJson = parseResource('{"resourceType":"Observation","status":"final"}').resource;
const fromXml = parseResourceXml(
  '<Observation xmlns="http://hl7.org/fhir"><status value="final"/></Observation>',
).resource;

nodesEquivalent(fromJson, fromXml); // => true

Write either format back out​

serializeResource writes JSON and serializeResourceXml writes XML, from either read:

import { parseResourceXml, serializeResource, serializeResourceXml } from "@cosyte/fhir";

const xml = '<Observation xmlns="http://hl7.org/fhir"><status value="final"/></Observation>';
const { resource } = parseResourceXml(xml);

serializeResource(resource); // => '{"resourceType":"Observation","status":"final"}'
serializeResourceXml(resource) === xml; // => true

A writer refuses, with a coded FhirSerializeError, rather than write something the model cannot spell faithfully in the target format. Troubleshooting lists what it refuses.

Reference​