• Jsonix (JSON interfaces for XML) is a JavaScript library which allows you to convert between XML and JSON structures.
• With Jsonix you can parse XML into JSON (this process is called unmarshalling) or serialize JSON in XML form (this is called marshalling).
• These conversions are based on declarative XML/JSON mappings which can be written manually or generated from an XML Schema.

Jsonix advantages:

• Strongly structured
• Type-safe
• Bidirectional
• (Optionally) XML Schema-driven

See also the other Jsonix features.

Here's a working example for the purchase order schema (try it online in JSFiddle).

java -jar node_modules/jsonix/lib/jsonix-schema-compiler-full.jar
  -d mappings -p PO purchaseorder.xsd

Generates mappings for the purchaseorder.xsd schema in the mappings\PO.js; mappings will be placed in the variable PO.

// Include or require PO.js so that PO variable is available
// For instance, in node.js:
var PO = require('./mappings/PO').PO;

// First we construct a Jsonix context - a factory for unmarshaller (parser)
// and marshaller (serializer)
var context = new Jsonix.Context([PO]);

// Then we create a unmarshaller
var unmarshaller = context.createUnmarshaller();

// Unmarshal an object from the XML retrieved from the URL
unmarshaller.unmarshalURL('po.xml',
    // This callback function will be provided
    // with the result of the unmarshalling
    function (unmarshalled) {
        // Alice Smith
        console.log(unmarshalled.value.shipTo.name);
        // Baby Monitor
        console.log(unmarshalled.value.items.item[1].productName);
    });

You can also unmarshalString, unmarshalDocument and (under node.js) unmarshalFile.

// Create a marshaller
var marshaller = context.createMarshaller();

// Marshal a JavaScript Object as XML (DOM Document)
var doc = marshaller.marshalDocument({
    name: {
        localPart: "purchaseOrder"
    },
    value: {
        orderDate: { year: 1999, month: 10, day: 20 },
        shipTo: {
            country: "US",
            name: "Alice Smith",
            street: "123 Maple Street",
            city: "Mill Valley",
            state: "CA",
            zip: 90952
        },
        billTo: { /* ... */ },
        comment: 'Hurry, my lawn is going wild!',
        items: { /* ... */ }
    }
});

You can also marshalString.

• Runs in almost any modern browser
• Runs in Node.js, package.json can be found here
• Runs with CommonJS modules, AMD modules as well as vanilla (globals, without any module loader)
• Bidirectional (XML -> JS as well as JS -> XML)
• Implements marshalling (serializing the JavaScript object into XML)
  • Supports string data and DOM nodes as result
• Implements unmarshalling (parsing a JavaScript object from XML)
  • Supports string data, DOM nodes, URLs or files (with Node.js) as source
• Driven by declarative XML/JS mappings which control how JavaScript object is converted into XML or vice versa
• Mappings can be automatically generated based on the XML Schema
• Strongly-structured - XML/object mappings describe structures of JavaScript objects
• Strongly-typed - Conversion between string content on XML side and values on the JavaScript side is controlled by declared property types
• Provides extensible type system
  • Supports most XML Schema simple types (inlcuding QNames)
  • Supports enumerations, list and union simple types
  • Allows adding own simple types
  • Supports complex types consisting of several properties
  • Supports deriving complex types by extension
• Provides advanced property system
  • Value, attribute, element, element reference properties for string processing of XML content
  • Any attribute, any element properties for "lax" processing for XML content

• Jsonix GitHub Project
• Jsonix Wiki

Jsonix is developed with WebStorm, the smartest JavaScript IDE.
Many thanks to JetBrains for providing a free open-source license for Jsonix development.