Converting JSON to XML

Why do we still need XML?

If you are building a modern web application in React, Vue, or Next.js, your entire stack speaks JSON. However, the moment your app needs to talk to a banking API, a government gateway, or an enterprise ERP (like SAP or Tally), you hit a wall: they require XML payloads wrapped in SOAP envelopes.

The Challenge with Arrays

Converting JSON to XML is not a 1:1 mapping. JSON uses brackets [] to define arrays of similar items. XML has no concept of an array; it simply repeats the same tag name multiple times.

// JSON Array
{
  "users": [
    { "name": "Alice" },
    { "name": "Bob" }
  ]
}

Must be explicitly mapped to repeat the child tag in XML:

<!-- XML Repetition -->
<users>
  <user>
    <name>Alice</name>
  </user>
  <user>
    <name>Bob</name>
  </user>
</users>

Using fast-xml-parser Builder

The easiest way to generate XML programmatically in Node.js is using the XMLBuilder from the fast-xml-parser library.

const { XMLBuilder } = require('fast-xml-parser');

const jsonPayload = {
    request: {
        "@_version": "1.0",
        user: [
            { name: "Alice", role: "Admin" },
            { name: "Bob", role: "Editor" }
        ]
    }
};

const builder = new XMLBuilder({
    ignoreAttributes: false,
    format: true
});

const xmlOutput = builder.build(jsonPayload);
console.log(xmlOutput);

Handling Attributes (@_)

Notice the "@_version" key in the JSON payload above? By convention, parsers use a prefix (usually @_) to differentiate between an XML node's text content and its attributes. When the builder runs, "@_version": "1.0" becomes <request version="1.0">.