Closing the XML Gap in TypeScript (for Localization Workflows)
If you’ve ever tried to process XML in Node.js or TypeScript, you’ve probably run into a limitation: parsing is easy, but validation against DTD or XML Schema is not.
That becomes a real problem when working with localization standards like TMX, XLIFF or SRX where structure and validity are not optional, they define whether your data is usable.
This is the gap I ran into and eventually decided to close.
The old setup: Java for XML
Localization standards such as TMX, XLIFF, SRX and TBX are all XML-based. When I started working with them more than 20 years ago, Java was the most practical choice. Its XML tooling wasn’t perfect, but it was reliable enough for parsing and validation.
That worked well for a long time.
The problem wasn’t XML; it was everything around it.
Java desktop UI options didn’t evolve in a way that fit my needs. I used SWT for years, but it became less maintained, and alternatives like Swing or JavaFX didn’t appeal to me.
Moving to TypeScript
Around 2018, I shifted toward building user interfaces with HTML, CSS and JavaScript. Eventually, TypeScript became the obvious choice because it provides a safer development model with static checks.
That solved the UI side.
But it created a new problem:
UI in TypeScript
XML processing still in Java
Maintaining two stacks for a single workflow wasn’t ideal.
The missing piece: XML validation in TypeScript
At the time, there were XML parsers in JavaScript, but none supported:
DTD validation
XML Schema validation
For localization formats, that’s a hard requirement. Without validation, you can’t guarantee that a TMX or XLIFF file is structurally correct.
So, I started building TypesXML, a native XML parser and validator for TypeScript.
A minimal example
Here’s what basic XML parsing looks like:
import { DOMBuilder, SAXParser } from "typesxml";
const handler = new DOMBuilder();
const parser = new SAXParser();
parser.setContentHandler(handler);
parser.parseFile("example.xml");
const document = handler.getDocument();
console.log(document.toString());
The same parser can be configured to:
validate against DTD
validate against XML Schema
resolve XML catalogs
This makes it possible to process XML in Node.js with the same level of control traditionally associated with Java libraries.
Building the missing stack
Creating a full XML stack took time:
DOM and SAX-style parsing came first
DTD validation followed
XML Schema validation was the final step
XML Schema support is significantly more complex, but it’s essential for formats like XLIFF.
Supporting pieces: language data
Localization workflows also depend heavily on language codes.
BCP47 defines the standard, but the official data is distributed as a large text file. To make it easier to use in TypeScript, I built TypesBCP47, a companion library that parses that data and exposes it in a structured way.
Proof of concept: rewriting existing tools
To validate the approach, I rewrote existing tools in TypeScript:
These tools:
process large XML files
validate against official grammars
maintain performance comparable to the original Java versions
That confirmed that TypeScript can handle real-world localization workloads.
XLIFF support
XLIFF uses XML Schema, which required implementing a full schema validator.
With that in place, I built TypesXLIFF, a library for parsing, generating, and validating XLIFF 2.x files.
It supports:
XML Schema validation
validation against the XLIFF specification
a typed object model
JSON conversion
What this enables
With these pieces in place, it’s now possible to:
Validate TMX, XLIFF, and SRX directly in Node.js
Build localization pipelines entirely in TypeScript
Remove the need for a separate Java backend
Keep both UI and processing in the same language
What’s next
TBX support is in progress, along with updates to other tools to move them fully to TypeScript.
Some Java code still exists in older components, but new development is now centered on TypeScript.
Closing thoughts
For a long time, XML processing in localization workflows effectively required Java.
That’s no longer the case.
If you’re working with XML-based formats in Node.js, especially in localization or structured data pipelines, you can now handle parsing, validation, and processing entirely in TypeScript.