nodehl7

NodeJS Library for parsing HL7 Messages

Homepage: https://loksly.github.io/nodehl7/

This library provides an easy way to parse HL7 Messages v.2.x, text-based, no XML format. Note there is another package named node-hl7 that provides a different API.

Features

✅ TypeScript Support: Full TypeScript definitions with type safety
✅ Typed Segment Definitions: Each segment (PID, MSH, OBX, etc.) has its own TypeScript type with typed field names for autocompletion
✅ Type-safe Segment Access: message.get('PID') returns a typed PIDSegment instead of a generic segment
✅ Promise-based API: Modern async/await support with backward-compatible callbacks
✅ Dual Module Format: Both CommonJS and ES Modules supported
✅ Event Emitter: Subscribe to parse events
✅ HL7 v2.x: Support for HL7 version 2.x text-based messages
✅ MLLP Network Transport: Built-in MLLP server and client for real-time HL7 message exchange over TCP/IP
✅ TLS/SSL Support: Optional encrypted connections for secure HL7 communication

Installation

npm install nodehl7 --save

Quick Start

Using Promises (Recommended)

const Hl7lib = require('nodehl7');
const hl7parser = new Hl7lib();

// Parse a file with async/await
async function parseHL7File() {
  try {
    const message = await hl7parser.parseFile('./path/to/file.hl7');
    
    const pidSegment = message.get('PID');
    const patientIDs = pidSegment.get('Patient identifier list');
    
    console.log(patientIDs);
  } catch (err) {
    console.error(err);
  }
}

// Parse message content directly
async function parseHL7String() {
  const hl7Content = "MSH|^~\\&|...";
  
  try {
    const message = await hl7parser.parse(hl7Content, 'message-id');
    console.log(message.get('MSH', 'Version ID'));
  } catch (err) {
    console.error(err);
  }
}

// Using .then() and .catch()
hl7parser.parseFile('./path/to/file.hl7')
  .then(message => {
    console.log(message.get('MSH', 'Sending application'));
  })
  .catch(err => {
    console.error(err);
  });

Using Callbacks (Legacy, still supported)

const Hl7lib = require('nodehl7');
const config = {
  "mapping": false,
  "profiling": true,
  "debug": true,
  "fileEncoding": "iso-8859-1"
};

let hl7parser = new Hl7lib(config);

let callback = function(err, message){
  if (err){
    console.error(err);
  } else {
    let pidSegment = message.get('PID');
    let patientIDs = pidSegment.get('Patient identifier list');
    
    console.log(patientIDs);
  }
};

hl7parser.parseFile(path, callback);

TypeScript Usage

import Hl7Parser from 'nodehl7';

const hl7parser = new Hl7Parser({
  fileEncoding: 'iso-8859-1'
});

async function parseFile(filepath: string) {
  const message = await hl7parser.parseFile(filepath);
  const versionId = message.get('MSH', 'Version ID');
  console.log(versionId);
}

MLLP Network Transport

The library includes built-in support for MLLP (Minimal Lower Layer Protocol), the standard transport protocol for HL7 v2.x messages over TCP/IP. MLLP wraps each HL7 message with framing bytes:

Start Block: 0x0B (VT - Vertical Tab)
Payload: The HL7 message
End Block: 0x1C (FS - File Separator) followed by 0x0D (CR - Carriage Return)

MLLP Server

const { MLLPServer } = require('nodehl7');

const server = new MLLPServer((message, reply) => {
  console.log('Received:', message.toString());
  // Send an ACK response
  reply('MSH|^~\\&|REC_APP||SEND_APP||202305101000||ACK|456|P|2.3\rMSA|AA|123');
});

server.listen(2575, '0.0.0.0', () => {
  console.log('MLLP server listening on port 2575');
});

You can also use the event-based API:

const server = new MLLPServer();

server.on('hl7_message', (message, reply) => {
  console.log('Received:', message.toString());
  reply('MSH|^~\\&|...||...||...||ACK|...\rMSA|AA|...');
});

server.listen(2575);

MLLP Client

const { MLLPClient } = require('nodehl7');

const client = new MLLPClient('127.0.0.1', 2575);

const hl7Message = 'MSH|^~\\&|SENDING_APP|SENDING_FAC|REC_APP|REC_FAC|202305101000||ADT^A01|123|P|2.3';

client.send(hl7Message).then(response => {
  console.log('ACK:', response.toString());
  client.close();
}).catch(err => {
  console.error('Error:', err);
  client.close();
});

MLLP with TLS/SSL

For secure encrypted connections, both server and client support optional TLS configuration:

const fs = require('fs');
const { MLLPServer, MLLPClient } = require('nodehl7');

// TLS Server
const server = new MLLPServer((message, reply) => {
  reply('MSH|^~\\&|...||...||...||ACK|...\rMSA|AA|...');
}, {
  tls: {
    key: fs.readFileSync('server-key.pem'),
    cert: fs.readFileSync('server-cert.pem')
  }
});

server.listen(2576, () => {
  console.log('Secure MLLP server listening on port 2576');
});

// TLS Client
const client = new MLLPClient('127.0.0.1', 2576, {
  tls: {
    rejectUnauthorized: true,
    ca: fs.readFileSync('ca-cert.pem')
  }
});

const response = await client.send(hl7Message);
console.log('ACK:', response.toString());
client.close();

TypeScript MLLP Usage

import { MLLPServer, MLLPClient } from 'nodehl7';

const server = new MLLPServer((message, reply) => {
  const hl7String = message.toString();
  console.log('Received:', hl7String);
  reply('MSH|^~\\&|...||...||...||ACK|...\rMSA|AA|...');
});

server.listen(2575, '0.0.0.0', () => {
  console.log('Server ready');
});

async function sendMessage() {
  const client = new MLLPClient('127.0.0.1', 2575);
  const response = await client.send('MSH|^~\\&|...');
  console.log(response.toString());
  client.close();
}

Testing

To run tests:

npm test

To run tests with code coverage:

npm run coverage

This will generate coverage reports in the coverage/ directory:

coverage/lcov.info - LCOV format for CI/GitHub Actions integration
coverage/lcov-report/index.html - HTML report for local viewing
coverage/coverage-final.json - JSON format for programmatic access

API Documentation

Hl7Parser

An hl7Parser is an EventEmitter so it provides events like:

error: Whenever a new error happens.
message: Whenever a new message has been parsed.
Event Type Code: Events named after the Event Type Code field from the EVN Segment (e.g., A01, A02, A03).

Constructor

new Hl7Parser(config?)

Configuration options:

mapping (boolean): Enable field mapping
profiling (boolean): Enable profiling
debug (boolean): Enable debug mode
fileEncoding (string): File encoding (default: 'utf8', example: 'iso-8859-1')
logger (Pick<Console, 'error'>): Custom logger object — must provide an error() method (defaults to console)
fs (Pick<typeof fs, 'stat' | 'open' | 'close' | 'read'>): Custom filesystem object — must provide stat, open, close, and read methods (defaults to Node.js fs)

Methods

`parse(messageContent, ID, callback?)`

Parses an HL7 message string.

Returns: Promise<Hl7Message>

Parameters:

messageContent (string): The HL7 message content
ID (string): An identifier for the message
callback (function, optional): Callback function (err, Hl7Message) => void

// Promise
const message = await hl7parser.parse(messageContent, 'msg-001');

// Callback
hl7parser.parse(messageContent, 'msg-001', (err, message) => {
  // ...
});

`parseFile(filepath, callback?)`

Parses an HL7 message from a file.

Returns: Promise<Hl7Message>

Parameters:

filepath (string): Path to the HL7 file
callback (function, optional): Callback function (err, Hl7Message) => void

// Promise
const message = await hl7parser.parseFile('./file.hl7');

// Callback
hl7parser.parseFile('./file.hl7', (err, message) => {
  // ...
});

Hl7Message

Methods

size(): Returns the number of segments in the message.
get(segmentname): Returns an Hl7Segment.
get(segmentname, fieldname): Returns a field value (can be a string, array, or null).
get(segmentname, fieldname, joinChar): Returns the field value. If it's an array, joins it using joinChar as separator.
getSegmentAt(index): Returns the segment at the specified position.
getSegments(segmentname): Returns all segments with the specified name.

const message = await hl7parser.parseFile('./file.hl7');

// Get a segment
const pidSegment = message.get('PID');

// Get a field value
const patientName = message.get('PID', 'Patient name');

// Get a field and join if array
const phoneNumbers = message.get('PID', 'Phone number (home)', ' / ');

// Get segment by index
const firstSegment = message.getSegmentAt(0);

// Get number of segments
const segmentCount = message.size();

Hl7Segment

Methods

get(fieldname): Returns a field value (can be a string, array, or null).
set(fieldname, value): Sets the value of a field.
toMappedObject(compact?): Converts the segment to a JavaScript object.

const pidSegment = message.get('PID');

// Get field value
const patientId = pidSegment.get('Patient identifier list');

// Set field value
pidSegment.set('Patient name', 'John Doe');

// Convert to object
const pidObject = pidSegment.toMappedObject();

MLLPServer

An MLLP server that handles incoming HL7 messages over TCP or TLS connections.

Constructor

new MLLPServer(handler?, options?)

Parameters:

handler (function, optional): A callback (message: Buffer, reply: Function) => void invoked for each received message
options (object, optional): Configuration options
- tls (object, optional): TLS options passed to tls.createServer() (e.g., { key, cert, ca })

Events:

'hl7_message' — Emitted with (message: Buffer, reply: Function, socket: net.Socket) when a complete MLLP-framed message is received

Methods:

listen(port, hostname?, callback?): Start listening for connections.
close(callback?): Stop accepting new connections and close the server.
address(): Returns the bound address of the server.

MLLPClient

A client for sending HL7 messages to an MLLP server and receiving responses.

Constructor

new MLLPClient(host, port, options?)

Parameters:

host (string): The server hostname or IP address
port (number): The server port
options (object, optional): Configuration options
- tls (object, optional): TLS options passed to tls.connect() (e.g., { rejectUnauthorized, ca })

Methods:

`send(data)`

Sends an HL7 message and waits for the server's response.

Returns: Promise<Buffer>

Parameters:

data (string | Buffer): The HL7 message to send

const response = await client.send(hl7Message);

`close()`

Closes the client connection.

MLLP Framing Utilities

Low-level utilities for MLLP message framing:

const { mllpWrap, mllpUnwrap } = require('nodehl7');

// Wrap a message with MLLP framing bytes
const framed = mllpWrap('MSH|^~\\&|...');

// Extract messages from a buffer containing MLLP-framed data
const { messages, remainder } = mllpUnwrap(framed);

Supported Segments

The library includes field mappings for 81 HL7 v2.x segments, providing comprehensive support for various healthcare message types:

Message Structure & Control (10 segments)

MSH - Message Header
MSA - Message Acknowledgment
ERR - Error
BHS - Batch Header Segment
BTS - Batch Trailer Segment
FHS - File Header Segment
FTS - File Trailer Segment
DSC - Continuation Pointer
DSP - Display Data
NDS - Notification Detail

Patient Demographics & Administration (13 segments)

PID - Patient Identification
PD1 - Patient Additional Demographic
NK1 - Next of Kin / Associated Parties
PV1 - Patient Visit
PV2 - Patient Visit - Additional Information
MRG - Merge Patient Information
DB1 - Disability
ACC - Accident
AL1 - Patient Allergy Information
UB1 - UB82 Data
UB2 - UB92 Data
DRG - Diagnosis Related Group
EVN - Event Type

Orders & Observations (10 segments)

ORC - Common Order
OBR - Observation Request
OBX - Observation/Result
NTE - Notes and Comments
TQ1 - Timing/Quantity
TQ2 - Timing/Quantity Relationship
CTI - Clinical Trial Identification
FT1 - Financial Transaction
BLG - Billing
ABS - Abstract

Clinical Procedures & Diagnosis (4 segments)

PR1 - Procedures
DG1 - Diagnosis
GOL - Goal Detail
PRB - Problem Details

Pharmacy & Medications (7 segments)

RXA - Pharmacy/Treatment Administration
RXD - Pharmacy/Treatment Dispense
RXE - Pharmacy/Treatment Encoded Order
RXG - Pharmacy/Treatment Give
RXO - Pharmacy/Treatment Order
RXC - Pharmacy/Treatment Component Order
RXR - Pharmacy/Treatment Route

Scheduling & Resources (6 segments)

SCH - Scheduling Activity Information
AIG - Appointment Information - General Resource
AIL - Appointment Information - Location Resource
AIP - Appointment Information - Personnel Resource
AIS - Appointment Information - Service
RGS - Resource Group

Staff & Personnel (3 segments)

STF - Staff Identification
PRA - Practitioner Detail
ROL - Role

Financial & Insurance (3 segments)

GT1 - Guarantor
IN1 - Insurance
IN2 - Insurance Additional Information

Query & Response (6 segments)

QRD - Query Definition
QRF - Query Filter
URD - Results/Unsolicited Display Update Definition
URS - Unsolicited Selection

Master Files & Observations (7 segments)

OM1 - General Segment
OM2 - Numeric Observation
OM3 - Categorical Service/Test/Observation
OM4 - Observations that Require Specimens
OM5 - Observation Batteries
OM6 - Observations that are Calculated
OM7 - Additional Basic Attributes

Documents & Reports (3 segments)

TXA - Transcription Document Header
PTH - Pathway
VAR - Variance

Dietary (2 segments)

ODS - Dietary Orders, Supplements, Preferences
ODT - Diet Tray Instructions

Specimen & Inventory (3 segments)

SPM - Specimen
SAC - Specimen Container Detail
INV - Inventory Detail

Product Experience & Safety (4 segments)

PEO - Product Experience Observation
PCR - Possible Causal Relationship
PSH - Product Summary Header
PDC - Product Detail Country

Facility & Security (2 segments)

FAC - Facility
CER - Certificate Data

Field Mappings Reference

Click to expand complete field mappings

HL7Segment.prototype.segmentsFields = {
		'MSH':
			['Encoding characters', 'Sending application', 'Sending facility', 'Receiving application',
			'Receiving facility', 'Date/time of message', 'Security', 'Message type', 'Message control ID', 'Processing ID',
			'Version ID', 'Sequence number', 'Continuation pointer', 'Accept acknowledgement type', 'Application acknowledgement type',
			'Country code', 'Character set', 'Principal language of message', 'Alternate character set handling'],
		'EVN':
			['Event Type Code', 'Recorded Date/Time', 'Date/Time Planned Event', 'Event Reason Code', 'Operator ID', 'Event Occurred', 'Event Facility'],
		'PID':
			['Set ID – PID', 'Patient ID', 'Patient identifier list', 'Alternate patient ID – PID', 'Patient name', 'Mother\'s maiden name',
			'Date of birth', 'Gender', 'Patient alias', 'Race', 'Patient Address', 'County code', 'Phone number (home)', 'Phone number –business',
			'Primary language', 'Marital status', 'Religion', 'Patient account number', 'SSN number – patient', 'Driver\'s license number – patient',
			'Mother\'s identifier', 'Ethnic group', 'Birth place', 'Multiple birth indicator', 'Birth order', 'Citizenship', 'Veterans military status',
			'Nationality', 'Patient death date', 'Patient death indicator'],
		'PV1':
			['Set ID - PV1', 'Patient Class', 'Assigned Patient Location', 'Admission Type', 'Preadmit Number', 'Prior Patient Location',
			'Attending Doctor', 'Referring Doctor', 'Consulting Doctor', 'Hospital Service', 'Temporary Location', 'Preadmit Test Indicator', 'Re-admission Indicator',
			'Admit Source', 'Ambulatory Status', 'VIP Indicator', 'Admitting Doctor', 'Patient Type', 'Visit Number', 'Financial Class', 'Charge Price Indicator',
			'Courtesy Code', 'Credit Rating', 'Contract Code', 'Contract Effective Date', 'Contract Amount', 'Contract Period', 'Interest Code',
			'Transfer to Bad Debt Code', 'Transfer to Bad Debt Date', 'Bad Debt Agency Code', 'Bad Debt Transfer Amount', 'Bad Debt Recovery Amount',
			'Delete Account Indicator', 'Delete Account Date', 'Discharge Disposition', 'Discharged to Location', 'Diet Type', 'Servicing Facility', 'Bed Status',
			'Account Status', 'Pending Location', 'Prior Temporary Location', 'Admit Date/Time', 'Discharge Date/Time', 'Current Patient Balance', 'Total Charges',
			'Total Adjustments', 'Total Payments', 'Alternate Visit', 'Visit Indicator', 'Other Healthcare Provider'],
		'PV2':
			['Prior Pending Location', 'Accommodation Code', 'Admit Reason', 'Transfer Reason', 'Patient Valuables', 'Patient Valuables Location', 'Visit User Code',
			'Expected Admit Date', 'Expected Discharge Date', 'Estimated Length of Inpatient Stay', 'Actual Length of Inpatient Stay', 'Visit Description', 'Referral Source Code',
			'Previous Service Date', 'Employment Illness Related Indicator', 'Purge Status Code', 'Purge Status Date', 'Special Program Code', 'Retention Indicator', 'Expected Number of Insurance Plans',
			'Visit Publicity Code', 'Visit Protection Indicator', 'Clinic Organization Name', 'Patient Status Code', 'Visit Priority Code', 'Previous Treatment Date', 'Expected Discharge Disposition',
			'Signature on File Date', 'First Similar Illness Date', 'Patient Charge Adjustment Code', 'Recurring Service Code', 'Billing Media Code', 'Expected Surgery Date & Time',
			'Military Partnership Code', 'Military Non-Availability Code', 'Newborn Baby Indicator', 'Baby Detained Indicator'],
		'OBX':
			['Set ID - OBX', 'Value Type', 'Observation Identifier', 'Observation Sub-ID', 'Observation Value', 'Units', 'References Range', 'Abnormal Flags', 'Probability',
			'Nature of Abnormal Test', 'Observ Result Status', 'Date Last Obs Normal Values', 'User Defined Access Checks', 'Date/Time of the Observation', 'Producer\'s ID',
			'Responsible Observer', 'Observation Method'],
		'DG1':
			['Set ID - DG1', 'Diagnosis Coding Method', 'Diagnosis Code', 'Diagnosis Description', 'Diagnosis Date/Time', 'Diagnosis/DRG Type', 'Major Diagnostic Category',
			'Diagnostic Related Group', 'DRG Approval Indicator', 'DRG Grouper Review Code', 'Outlier Type', 'Outlier Days', 'Outlier Cost', 'Grouper Version and Type',
			'Diagnosis/DRG Priority', 'Diagnosing Clinician', 'Diagnosis Classification', 'Confidential Indicator', 'Attestation Date/Time'],
		'ORC':
			['Order Control', 'Placer Order Number', 'Filler Order Number', 'Placer Group Number', 'Order Status', 'Response Flag', 'Quantity/Timing', 'Parent', 'Date/Time of Transaction',
			'Entered By', 'Verified By', 'Ordering Provider', 'Enterer\'s Location', 'Call Back Phone Number', 'Order Effective Date/Time', 'Order Control Code Reason',
			'Entering Organization', 'Entering Device', 'Action By'],
		'PR1':
			['Set ID - PR1', 'Procedure Coding Method', 'Procedure Code', 'Procedure Description', 'Procedure Date/Time', 'Procedure Type', 'Procedure Minutes', 'Anesthesiologist',
			'Anesthesia Code', 'Anesthesia Minutes', 'Surgeon', 'Procedure Practitioner', 'Consent Code', 'Procedure Priority', 'Associated Diagnosis Code'],
		'PD1':
			['Living Dependency', 'Living Arrangement', 'Patient Primary Facility', 'Patient Primary Care Provider Name & ID No.', 'Student Indicator', 'Handicap', 'Living Will',
			'Organ Donor', 'Separate Bill', 'Duplicate Patient', 'Publicity Indicator', 'Protection Indicator'],
		'AL1':
			['Set ID - AL1', 'Allergen Type Code', 'Allergen Code/Mnemonic/Description', 'Allergy Severity Code', 'Allergy Reaction Code', 'Identification Date'],
		'MRG':
			['Prior Patient ID - Internal', 'Prior Alternate Patient ID', 'Prior Patient Account Number', 'Prior Patient ID - External', 'Prior Visit Number', 'Prior Alternate Visit ID', 'Prior Patient Name'],
		'GT1':
			['Set ID - GT1', 'Guarantor Number', 'Guarantor Name', 'Guarantor Spouse Name', 'Guarantor Address', 'Guarantor Ph Num- Home', 'Guarantor Ph Num-Business',
			'Guarantor Date/Time of Birth', 'Guarantor Sex', 'Guarantor Type', 'Guarantor Relationship', 'Guarantor SSN', 'Guarantor Date - Begin', 'Guarantor Date - End', 'Guarantor Priority',
			'Guarantor Employer Name', 'Guarantor Employer Address', 'Guarantor Employ Phone Number', 'Guarantor Employee ID Number', 'Guarantor Employment Status', 'Guarantor Organization',
			'Guarantor Billing Hold Flag', 'Guarantor Credit Rating Code', 'Guarantor Death Date And Time', 'Guarantor Death Flag', 'Guarantor Charge Adjustment Code', 'Guarantor Household Annual Income',
			'Guarantor Household Size', 'Guarantor Employer ID Number', 'Guarantor Marital Status Code', 'Guarantor Hire Effective Date', 'Employment Stop Date', 'Living Dependency', 'Ambulatory Status',
			'Citizenship', 'Primary Language', 'Living Arrangement', 'Publicity Indicator', 'Protection Indicator', 'Student Indicator', 'Religion', 'Mother\'s Maiden Name', 'Nationality', 'Ethnic Group',
			'Contact Person\'s Name', 'Contact Person\'s Telephone Number', 'Contact Reason', 'Contact Relationship Code', 'Job Title', 'Job Code/Class', 'Guarantor Employer\'s Organization Name', 'Handicap',
			'Job Status', 'Guarantor Financial Class', 'Guarantor Race'],
		'OBR':
			['Set ID - OBR', 'Placer Order Number', 'Filler Order Number', 'Universal Service ID', 'Priority', 'Requested Date/time', 'Observation Date/time', 'Observation End Date/time',
			'Collection Volume', 'Collector Identifier', 'Specimen Action Code', 'Danger Code', 'Relevant Clinical Info', 'Specimen Received Date/Time', 'Specimen Source', 'Ordering Provider',
			'Order Callback Phone Number', 'Placer field 1', 'Placer field 2', 'Filler Field 1', 'Filler Field 2', 'Results Rpt/Status Chng - Date/Time', 'Charge to Practice', 'Diagnostic Serv Sect ID',
			'Result Status', 'Parent Result', 'Quantity/Timing', 'Result Copies To', 'Parent', 'Transportation Mode', 'Reason for Study', 'Principal Result Interpreter', 'Assistant Result Interpreter',
			'Technician', 'Transcriptionist', 'Scheduled Date/Time', 'Number of Sample Containers', 'Transport Logistics of Collected Sample', 'Collector\'s Comment', 'Transport Arrangement Responsibility',
			'Transport Arranged', 'Escort Required', 'Planned Patient Transport Comment'],
		'NTE':
			['Set ID - NTE', 'Source of Comment', 'Comment', 'Comment Type'],
		'NK1':
			['Set ID - NK1', 'Name', 'Relationship', 'Address', 'Phone Number', 'Business Phone Number', 'Contact Role', 'Start Date', 'End Date', 'Next of Kin / Associated Parties Job Title',
			'Next of Kin / Associated Parties Job Code/Class', 'Next of Kin / Associated Parties Employee Number', 'Organization Name', 'Marital Status', 'Sex', 'Date/Time of Birth'],
		'IN1':
			['Set ID - IN1', 'Insurance Plan ID', 'Insurance Company ID', 'Insurance Company Name', 'Insurance Company Address', 'Insurance Co. Contact Person', 'Insurance Co Phone Number',
			'Group Number', 'Group Name', 'Insured\'s Group Emp ID', 'Insured\'s Group Emp Name', 'Plan Effective Date', 'Plan Expiration Date', 'Authorization Information', 'Plan Type',
			'Name Of Insured', 'Insured\'s Relationship To Patient', 'Insured\'s Date Of Birth', 'Insured’s Address', 'Assignment Of Benefits', 'Coordination Of Benefits', 'Coord Of Ben. Priority',
			'Notice Of Admission Flag', 'Notice Of Admission Date', 'Report Of Eligibility Flag', 'Report Of Eligibility Date', 'Release Information Code', 'Pre-Admit Cert (PAC)',
			'Verification Date/Time', 'Verification By', 'Type Of Agreement Code', 'Billing Status', 'Lifetime Reserve Days', 'Delay Before L.R. Day', 'Company Plan Code', 'Policy Number',
			'Policy Deductible', 'Policy Limit - Amount', 'Policy Limit - Days', 'Room Rate - Semi-Private', 'Room Rate - Private', 'Insured’s Employment Status', 'Insured\'s Sex',
			'Insured\'s Employer Address', 'Verification Status', 'Prior Insurance Plan ID', 'Coverage Type', 'Handicap', 'Insured’s ID Number']
	}

Migration Guide

From v1.x to v2.0.0

Version 2.0.0 introduces typed segment definitions and stricter TypeScript types. Most users won't need any code changes — this is only a concern if you pass custom logger or fs options.

Custom logger — Must now satisfy Pick<Console, 'error'>:

// Before (any object was accepted)
new Hl7Parser({ logger: myLogger });

// After (must have an error() method compatible with Console.error)
const myLogger = { error: (...args: any[]) => { /* ... */ } };
new Hl7Parser({ logger: myLogger });

Custom fs — Must now satisfy Pick<typeof fs, 'stat' | 'open' | 'close' | 'read'>:

// Must provide stat, open, close, and read methods
new Hl7Parser({ fs: myCustomFs });

Typed segment access — message.get('PID') now returns PIDSegment | null instead of HL7Segment | null for known segment names:

const pid = message.get('PID'); // PIDSegment | null
const name = message.get('PID', 'Patient name'); // string | string[] | null

From Callbacks to Promises

If you're upgrading from an older version, the API is fully backward compatible. You can migrate to promises gradually:

Before (Callbacks):

hl7parser.parseFile('./file.hl7', (err, message) => {
  if (err) return console.error(err);
  console.log(message.get('MSH', 'Version ID'));
});

After (Promises):

try {
  const message = await hl7parser.parseFile('./file.hl7');
  console.log(message.get('MSH', 'Version ID'));
} catch (err) {
  console.error(err);
}

Contributing

Contributions are welcome! Here's how you can help:

How to Contribute

Fork the repository and create your branch from master.
Install dependencies: npm install
Make your changes in the src/ directory.
Add tests for any new functionality in the test/ directory.
Run tests: npm test to ensure all tests pass.
Run coverage: npm run coverage to check code coverage.
Submit a pull request with a clear description of your changes.

Reporting Issues

Use the GitHub Issues page to report bugs.
Include a clear description of the issue, steps to reproduce, and expected behavior.
If possible, include a sample HL7 message that demonstrates the problem.

Development Setup

git clone https://github.com/Loksly/nodehl7.git
cd nodehl7
npm install
npm test

Code Style

Follow the existing code style and conventions.
Use TypeScript for all source files in src/.
Ensure TypeScript compiles without errors before submitting.

License

MIT

Credits

Original author: Loksly

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lib		lib
src		src
test		test
.eslintrc		.eslintrc
.gitignore		.gitignore
CHANGELOG.md		CHANGELOG.md
LICENSE		LICENSE
README.md		README.md
_config.yml		_config.yml
package-lock.json		package-lock.json
package.json		package.json
tsconfig.esm.json		tsconfig.esm.json
tsconfig.json		tsconfig.json

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nodehl7

Features

Installation

Quick Start

Using Promises (Recommended)

Using Callbacks (Legacy, still supported)

TypeScript Usage

MLLP Network Transport

MLLP Server

MLLP Client

MLLP with TLS/SSL

TypeScript MLLP Usage

Testing

API Documentation

Hl7Parser

Constructor

Methods

parse(messageContent, ID, callback?)

parseFile(filepath, callback?)

Hl7Message

Methods

Hl7Segment

Methods

MLLPServer

Constructor

MLLPClient

Constructor

send(data)

close()

MLLP Framing Utilities

Supported Segments

Message Structure & Control (10 segments)

Patient Demographics & Administration (13 segments)

Orders & Observations (10 segments)

Clinical Procedures & Diagnosis (4 segments)

Pharmacy & Medications (7 segments)

Scheduling & Resources (6 segments)

Staff & Personnel (3 segments)

Financial & Insurance (3 segments)

Query & Response (6 segments)

Master Files & Observations (7 segments)

Documents & Reports (3 segments)

Dietary (2 segments)

Specimen & Inventory (3 segments)

Product Experience & Safety (4 segments)

Facility & Security (2 segments)

Field Mappings Reference

Migration Guide

From v1.x to v2.0.0

From Callbacks to Promises

Contributing

How to Contribute

Reporting Issues

Development Setup

Code Style

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`parse(messageContent, ID, callback?)`

`parseFile(filepath, callback?)`

`send(data)`

`close()`

Packages