node-edifact

Currently supported functionality:

• An ES6 streaming parser reading UN/EDIFACT messages.
• Provide your own event listeners to get the parser to do something useful.
• Construct structured javascript objects from UN/EDIFACT messages.
• Support for the UNA header and custom separators.
• Validating data elements and components accepted by a given segment.
• Parsing and checking standard UN/EDIFACT messages with segment tables.

This library further intends to support:

• Writing and constructing UN/EDIFACT messages.
• Out of the box support for envelopes.

Usage

This example parses a document and translates it to a javascript array result containing segments. Each segment is an object containing a name and an elements array. An element is an array of components.

var Parser = require('edifact/parser.js');
var Validator = require('edifact/validator.js');

var doc = ...;

var validator = new Validator();
var parser = new Parser(validator);

// Provide some segment and element definitions.
validator.define(...);

// Parsed segments will be collected in the result array.
var result = [], elements, components;

parser.on('opensegment', function (segment) {
  // Started a new segment.
  elements = [];
  result.push({ name: segment, elements: elements });
});

parser.on('element', function () {
  // Parsed a new element.
  components = [];
  elements.push(components);
});

parser.on('component', function (data) {
  // Got a new component.
  components.push(value);
});

parser.on('closesegment', function () {
  // Closed a segment.
});

parser.write(doc)
parser.end();

Installation

The module can be installed through:

npm install edifact

Its only dependency is the node events library. Keep in mind that this is an ES6 library. It currently can be used with node 6.4 or higher. A suite of tests is included which can be run with the jasmine-es6 package.

Overview

This module is built around a central Parser class which provides the core UN/EDIFACT parsing functionality. It exposes two methods, the write() method to write some data to the parser and the end() method to close an EDI interchange. Data read by the parser can be read by using hooks which will be called on specific parsing events.

Configuring the parser

The Parser class currently supports any of the UNOA, UNOB, UNOC, UNOY and UCS2 encoding levels. Furthermore, the parser will read any custom delimiters from the UNA header. If such a header is not present in the document, the delimiters can also be configured manually. The delimiters should be specified using their character codes. An example:

let parser = new Parser();

parser.encoding('UNOC');
parser.configure({
  segmentTerminator: 39,
  dataElementSeparator: 43,
  componentDataSeparator: 58,
  decimalMark: 46,
  releaseCharacter: 63,
});

Parsing events

The parser can be used by listening to the following events:

Event	Description
opensegment	A new segment is started. The name of the segment is passed as the argument.
element	A new element is added. This only marks the start of the element, the data will follow through the component events.
component	A component is added to the element. The data is passed on as an argument.
closesegment	The current segment is terminated.

For all textual fields the data will be passed on literally to the component event handler. For numeric fields, the decimal mark will be replaced by a point (12,4 becomes 12.4 if the decimal mark is a comma). Keep in mind though that all components will be parsed as alphanumeric fields unless a validator is used! Only if the component is defined as numeric in the validator can it be parsed as such.

Converting EDIFACT to JSON

While the Parser class offers a flexible option to write your own EDIFACT applications, you might only be looking for an easy way read EDIFACT documents. The Reader class offers an easy to use interface:

let reader = new Reader({ autoDetectEncoding: true });
let result = reader.parse(document);

The parse() method returns an array of segments. Each segment is an object containing a segment name and the list of elements as an array of arrays with the actual component data.

Performance

Parsing speed including validation but without matching against a segment table is around 20Mbps. Around 30% of the time spent seems to be needed for the validation part.

If performance is critical the event callbacks can also be directly defined as methods on the Parser instance. Defining an event callback on('opensegment', callback) then becomes:

let parser = new Parser();
let callback = function (segment) { ... };

parser.onopensegment = callback;

Keep in mind that this avoids any opensegment events to be produced and as such, also its associated overhead.

Message validation

The validation of the message can be seen as two independent tasks:

• On the one hand the data contained in the elements and components need to be validated against their format.
• On the other hand the structure of the segments needs to be validated.

Data validation

Validation of the element and component data can be achieved through the Validator class:

var validator = new Validator();
var parser = new Parser();

validator.define(segments);
validator.define(elements);

However the Validator instance will only validate elements and components from segments and elements with a corresponding definition. These definitions can be provided through the define() method. Read on to learn more about their syntax.

Segment and element definitions

Definitions can be provided to describe the structure of segments and elements. An example of a segment definition:

{
  "BGM": {
    "requires": 0,
    "elements": ["C002", "C106", "1225", "4343"]
  }
}

The elements array contains the names of the elements that should be provided. The requires property indicates the number of elements which are required to obtain a valid segment. Any additional elements are considered optional. Definitions can also be provided to define the structure of the elements:

{
  "C002": {
    "requires": 4,
    "components": ["an..3", "an..17", "an..3", "an..35"]
  },
  "C106": {
    "requires": 3,
    "components": ["an..35", "an..9", "an..6"]
  }
}

An incomplete set of definitions is included with the library in the files segments.js and elements.js and can be included as follows:

var segments = require('edifact/segments');
var elements = require('edifact/elements');

A working example using segment and element definitions can be found in the examples directory.

Structural validation

Using a parser in conjuction with a Validator instance allows validation of isolated segments, elements and components. However, the parser can also be extended to validate the message structure. This can be accomplished by using a Tracker instance that will validate the received segments against a segment table. A set of example EDIFACT messages is included in the module in JSON format. To extend your parser, the segment can be passed on to the Tracker in the opensegment event handler:

var table = require('edifact/messages/APERAK');

var parser = new Parser();
var tracker = new Tracker(table);

parser.on('opensegment', function (segment) {
  if (tracker.accept(segment)) doSomething(); // The segment matches.
});

tracker.on('error', function (segment) {
  // Handle the error. Reject the message or ignore the segment.
});

Invalid input will generally fall in one of the following categories:

• A mandatory segment is skipped.
• An invalid segment is provided in the input.
• A segment is repeated too much.

However, the Tracker instance cannot generally discern between those cases since it will simply run through the segment table until a match is found. It will as a consequence fail in one of the following ways:

• The end of the segment table is reached.
• The provided segment doesn't match a mandatory segment in the segment table.
• If either of the above conditions results from a segment that exceeded its allowed number of repetitions, the Tracker instance will detect this and trigger a more appropriate error.

When such a situation is encountered, an error event will be fired. It is up to the user to handle the error. In the error handler, the current segment can be accessed through this.segment. The current position in the segment table can be retrieved through this.pointer.

If you want to build your own segment tables, please take a look in the messages folder to get the syntax right. Every segment in the segment table is of the following format:

{ "content": "UNH", "mandatory": true, "repetition": 1 }

A segment group can be written as follows:

{ "content": [
  { "content": "NAD", "mandatory": true, "repetition": 1 },
  { "content": "CTA", "mandatory": false, "repetition": 9 },
  { "content": "COM", "mandatory": false, "repetition": 9 }
], "mandatory": false, "repetition": 9 }

Classes

Class	Description
Parser	The Parser class encapsulates an online parsing algorithm. By itself it doesn't do anything useful, however the parser can be extended through several event callbacks.
Reader	The Reader offers a fast an easy to use interface to convert EDIFACT messages to a JSON structure.
Tracker	A utility class which validates segment order against a given message structure.
Validator	The Validator can be used as an add-on to the Parser class, to enable validation of segments, elements and components. This class implements a tolerant validator, only segments and elements for which definitions are provided will be validated. Other segments or elements will pass through untouched. Validation includes: Checking data element counts, including mandatory elements. Checking component counts, including mandatory components. Checking components against their required format.
Counter	The Counter class can be used as a validator for the Parser class. However it doesn't perform any validation, it only keeps track of segment, element and component counts. Component counts are reset when starting a new element, just like element counts are reset when closing the segment.

Reference

Parser

A parser capable of accepting data formatted as an UN/EDIFACT interchange. The constructor accepts a Validator instance as an optional argument:

new Parser([validator])

Function	Description
configure(config)	Configure any custom delimiters
encoding(level)	Set one of the predefined encoding levels
on(event,callback)	Add a listener for a specific event. The event can be any of opensegment, element, component and closesegment
write(chunk)	Write a chunk of data to the parser
end()	Terminate the EDI interchange

Reader

The Reader offers a fast an easy to use interface to convert EDIFACT messages to a JSON structure. Furthermore, the Reader class can also autodetect the message encoding (this feature can be turned off by passing autoDetectEncoding: false as an option to the constructor).

new Reader(options)

Function	Description
parse(document)	Parse a document and return the result as an array of segments.
define(definitions)	Provide the underlying Validator instance with definitions.

Tracker

A utility class which validates segment order against a given message structure. The constructor accepts a segment table as it's first argument:

new Tracker(table)

Function	Description
accept(segment)	Match a segment to the message structure and update the current position of the tracker
on(event,callback)	Use this to add a listener for the error event
reset()	Reset the tracker to the initial position of the current segment table

Validator

The Validator can be used to validate segments, elements and components. It keeps track of element and component counts and will ensure the correct data syntax.

Note that the Validator will not throw any errors though, since it only keeps the Parser from consuming any invalid data. It will be the parser that throws the error when it encounters data that it cannot consume.

new Validator()

Function	Description
disable()	Disable validation
enable()	Enable validation
define(definitions)	Provision the validator with an array of segment and element definitions
onopensegment(segment)	Start validation of a new segment
onelement()	Add an element
onopencomponent(tokenizer)	Open a component
onclosecomponent(tokenizer)	Close a component
onclosesegment()	Finish the segment

The tokenizer argument to both onopencomponent() and onclosecomponent() should provide three methods alpha(), alphanumeric(), and numeric() allowing the mode of the buffer to be set. It should also expose a length property to check the length of the data currently in the buffer.

Counter

The Counter class implements the same interface as the Validatorclass and can also be used as a validator when constructing a newParser` instance. However it doesn't perform any validation. It only keeps track of segment, element and component counts. Component counts are reset when starting a new element, just like element counts are reset when closing the segment.

new Counter()

Function	Description
onopensegment()	Start a new segment
onelement()	Add an element
onopencomponent()	Open a component
onclosecomponent()	Close a component
onclosesegment()	Finish the segment