How to parse X12 ISA/GS/ST envelopes and extract transaction sets in Node.js?

[hello-ediflow]

I receive X12 interchange files that contain ISA/GS/ST envelope segments wrapping multiple transaction sets. I need to:

• Parse the ISA (Interchange Control Header) for sender/receiver
• Parse GS (Functional Group) for version info
• Extract individual ST/SE transaction sets
• Handle both element and segment delimiters

[hello-ediflow]

EDIFlow handles X12 envelope parsing automatically:

npm install @ediflow/x12 @ediflow/x12-004010

import {
  X12MessageParser,
  X12DelimiterDetector,
  X12Tokenizer,
  X12SegmentParser,
} from '@ediflow/x12';

const parser = new X12MessageParser(
  new X12DelimiterDetector(),
  new X12Tokenizer(),
  new X12SegmentParser(),
);

const message = parser.parse(x12Interchange);

// ISA fields are accessible as envelope segments
const isa = message.segments.find(s => s.tag === 'ISA');
console.log(`Sender: ${isa?.elements[5]?.value}`);
console.log(`Receiver: ${isa?.elements[7]?.value}`);

// GS functional group
const gs = message.segments.find(s => s.tag === 'GS');
console.log(`Version: ${gs?.elements[7]?.value}`);  // '004010'

// Transaction content
console.log(`Type: ${message.messageType.value}`);  // '850'

The delimiter detector automatically identifies the element separator (often *), segment terminator (~), and sub-element separator (: or >).