SDC-Template-based Extract
A Typescript reference implementation of the $extract operation from the HL7 FHIR Structured Data Capture Specification. This only covers template-based extraction.
Usage
There are two ways to use this package:
- Using it in a web app
- Using it in a backend service e.g. ExpressJS
Using it in a web app
It is recommended to use inAppExtraction(), which performs an in-app extraction. This means that the app is not sending data to an external server, but rather using JavaScript to perform the extraction in the browser.
const responseToExtract = structuredClone(savedResponse); // Good practice to deep clone the response to prevent mutating the original response
const inAppExtractOutput = await inAppExtract(
responseToExtract,
sourceQuestionnaire
);
const { extractResult, extractSuccess } = inAppExtractOutput;
// Extraction is successful
if (extractSuccess && !extractResultIsOperationOutcome(extractResult)) {
const extractedBundle = extractResult.extractedBundle;
// Do things with the successfully extracted transaction bundle...
}
Available parameters for inAppExtract():
| Parameter | Description |
|---|---|
questionnaireResponse | QuestionnaireResponse to extract data from |
questionnaireOrCallback | Either a Questionnaire resource or a fetch/callback configuration for dynamic retrieval (if module making the inAppExtract() call does not have access to the Questionnaire resource). |
comparisonSourceResponse | An optional QuestionnaireResponse used for comparison when extracting. If this is provided, only "modified" items will be extracted. In most cases, this likely is the pre-populated response. |
Using it in a backend service
Using this library in a backend service requires more pre-configuration.
Due to how the $extract works, you will need to provide a Parameters resource defining the input parameters conforming to the extract() function.
sdc-template-extract allows you to specify custom questionnaire and comparison-source-response parameters, allowing you to pass their respective resources directly to the extract() function.
A library function createInputParameters() is provided to help you create the Parameters resource.
There is no sample implementation of using the extract() function in a backend service as of now.
Local development notes
It's recommended to run this library within a web app or a service if you're doing local development. This library compiles to both CommonJS and ES Modules, so there is no problems in using it across web frameworks and Node-based backends.
To compile the code, use npm run compile.
To watch for changes, use npm run watch.
Note: Do not use tsc or tsc -w as it will only compile to ES Modules, which means it will not work with CommonJS-based implementations.