FHIRPath

API

evaluate

Returns a JS object/primitive based on the evaluation.

evaluate(
  expression: string,
  ctx: unknown,
  options?: Options
): NonNullable<unknown>[]

evaluateWithMeta

Returns a @haste-health/meta-value singular value which contains data along with metadata about the evaluation.

function evaluateWithMeta(
  expression: string,
  ctx: unknown,
  options?: Options
): MetaValueSingular<NonNullable<unknown>>[];

Arguments

| name | type | description | | ------------------ | ---------------------------------------------------------------- | ------------------------------------------------------------------------------------------ | | expression | string | FHIRPath expression to evaluate. | | ctx | unknown | The context which the fhirpath is being evaluated from (sets $this context). | | options | Object | Includes variables and metadata deriviation functions. | | options.variables | Object | Function | If an object is Record<variableName, variableValue> else (variableName)=> variableValue. | | options.meta | Object | MetaInformation used to zip metadata with value. Used in type functions and operators. | | options.meta.type | string | Root type for ctx. | | options.meta.getSD | (fhir_version: FHIRVersion, type: string) => StructureDefinition | Returns a StructureDefinition based on type passed in. |

Usage

import * as fhirpath from "@haste-health/fhirpath";

// Default returns javascript object.
expect(fhirpath.evaluate("4 + 5", {})).toEqual([9]);
expect(fhirpath.evaluate("$this.test + 2 * 4", { test: 4 })).toEqual([12]);

// Evaluation with metavalue return (returns value in addition to meta information.)
expect(
  evaluateWithMeta(
    "$this.name",
    {
      resourceType: "Patient",
      name: [{ given: ["bob"], family: "jameson" }],
    },
    {
      meta: {
        type: "Patient",
        getSD: (fhirVersion, type: code) => {
          const foundSD = sds.find((sd) => sd.type === type);
          return foundSD;
        },
      },
    }
  ).map((v) => v.meta()?.type)
).toEqual(["HumanName"]);

Operations supported

| Operation | Description | Supported | | ------------------------- | -------------------------------------------------------------------------------------------- | --------- | | + (addition) | Concatenate strings or add values if numeric. | true | | - (subtraction) | Subtracts the right operand from the left operand. | true | | as type specifier | Returns left operand if value is of type specified. | true | | is(type : type specifier) | Filters left operand based on type specifier. | true | | * (multiplication) | Multiplies both arguments. | true | | / (division) | Divides the left operand by the right operand | true | | | (union collections) | Merge the two collections into a single collection | true | | = (Equals) | Returns true if the left collection is equal to the right collection | true | | != (Not Equals) | Converse operator of equals returns true if left collection is not equal to right collection | true |

Supported Functions

| Name | Description | Supported | | ---------- | ------------------------------------------------------------------------------------------------------------- | --------- | | empty | Returns true if the input collection is empty ({ }) and false otherwise. | true | | exists | Returns true if the collection has any elements, and false otherwise. | true | | all | Returns true if for every element in the input collection, criteria evaluates to true. | true | | allTrue | Takes a collection of Boolean values and returns true if all the items are true. | true | | anyTrue | Takes a collection of Boolean values and returns true if any of the items are true. | true | | allFalse | Takes a collection of Boolean values and returns true if all the items are false. | true | | anyFalse | Takes a collection of Boolean values and returns true if any of the items are false. | true | | subsetOf | Returns true if all items in the input collection are members of the collection passed in. | true | | supersetOf | Returns true if all items in the collection passed as the other argument are members of the input collection. | true | | count | Returns the integer count of the number of items in the input collection. | true | | distinct | Returns a collection containing only the unique items in the input collection. | true | | isDistinct | Returns true if all the items in the input collection are distinct. | true | | where | Returns a collection containing only those elements in the input collection based on where expression. | true | | select | Evaluates the projection expression for each item in the input collection. | true | | repeat | A version of select that will repeat the projection and add it to the output collection. | true | | ofType | Returns a collection that contains all items in the input collection that are of the given type. | true | | as | Returns filter same as ofType used for backwards compatibility. | true |