XML Processing

ES-Runtime includes a highly optimized native XML parser accessible via the runtime:serialization module. These operations run directly in Rust, completely avoiding JavaScript garbage collection overhead and offering best-in-class performance.

Parsing XML

Use XML.parse to convert an XML string directly into a JavaScript object.

JavaScript

import { XML } from "runtime:serialization";

const xmlData = `<user id="1"><name>Alice</name></user>`;

const parsed = XML.parse(xmlData);
console.log(parsed.name.$text); // "Alice"
console.log(parsed["@id"]);     // "1"

Validating XML

Use XML.validate to check if an XML string is well-formed.

JavaScript

import { XML } from "runtime:serialization";

const xmlData = `<user id="1"><name>Alice</name></user>`;

if (XML.validate(xmlData)) {
  console.log("XML is valid!");
}

const result = XML.validate("<invalid><xml>", { detailed: true });
console.log(result.valid); // false
console.log(result.error); // "Validation failed: ..."

Building XML

Use XML.build to serialize a JavaScript object back into an XML string.

JavaScript

import { XML } from "runtime:serialization";

const obj = {
  user: {
    "@id": "1",
    name: "Alice"
  }
};

const built = XML.build(obj);
console.log(built); // <user id="1"><name>Alice</name></user>

Streaming (XML.DecoderStream)

For massive multi-gigabyte XML datasets, ES-Runtime provides XML.DecoderStream. This is a standard Web TransformStream that consumes XML string chunks and incrementally yields fully-parsed JavaScript objects, achieving a near-zero memory footprint.

JavaScript

import { XML } from "runtime:serialization";

async function processMassiveFeed(fileStream) {
  // Pipe the chunks directly into the native streaming parser
  const objectStream = fileStream.pipeThrough(new XML.DecoderStream());

  // Use async iteration to consume parsed top-level element objects natively
  for await (const value of objectStream) {
    console.log(value);
  }
}

Performance

Because parsing happens directly within the Rust native core, runtime:serialization operates around 10% faster than fast-xml-parser running on Node.js or Bun, while utilizing half the memory. You can view the full benchmarks on the Benchmarks page.