FHIRPath

API

evaluate

Returns a JS object/primitive based on the evaluation.

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

evaluateWithMeta

Returns a @iguhealth/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 "@iguhealth/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