It's kind of tough to convert XML directly to other formats (including, but not limited to, JSON), because there are a lot of XML features that don't map cleanly onto JSON, such as:

• Text nodes (especially whitespace text nodes)

• Comments

• Attributes vs. child nodes

• Ordering of child nodes

As it happens, XSLT 3.0 and XPath 3.0 both have well documented and stable features for doing exactly this. Roundtripping XML to JSON and back is a solved problem - check it out some time; it may surprise you.

Are you talking about json-to-xml and xml-to-json?

From the XSLT spec [0]:

"Converts an XML tree, whose format corresponds to the XML representation of JSON defined in this specification, into a string conforming to the JSON grammar"

It can't take an arbitrary XML document and turn it into JSON, it can only take XML documents that conform to a specific format.

You can safely round-trip from JSON to XML and back to JSON. That's trivial because JSONs feature set is a subset of XMLs.

What you can't safely do is round-trip from arbitrary XML to JSON and back to XML. That's because, as the parent said, there are features in XML that don't exist in JSON. That means you are forced to find a way to encode it using the features you do have, but then you can't tell your encoding apart from valid values.

[0] https://www.w3.org/TR/xslt-30/#func-xml-to-json

You could conceivably serialize the DOM as a JSON object, but the representation would be very difficult to work with:

    {
      "type": "element",
      "name": "blink",
      "attributes": {
        "foo": "bar"
      },
      "children": [
        {
          "type": "text",
          "content": "example text"
        }
      ]
    }