JS-USE: XMLParser

const fs = require('fs');
const {Parser} = require('node-expat');
const {Writable} = require('stream');

class XMLParser extends Writable {

    constructor() {
        super();
        this.stages = [''];
        this.parser = new Parser('UTF-8');
        this.elements = [];

        this.findingState = {
            startElement: (tag, attributes) => {
                this.stages.push(tag);
                const path = this.stages.join('/');
                if (this.events.includes(path)) {
                    this.recordingState.startElement(tag, attributes);
                    this.currentState = this.recordingState;
                }
            },
            text: () => {
                // nothing
            },
            endElement: (tag) => {
                this.stages.pop();
            }
        }

        this.recordingState = {
            startElement: (tag, attributes) => {
                const element = {
                    "tag": tag,
                    "attributes": attributes,
                    "nodes": {},
                    "text": "",
                };
                if (this.elements.length > 0) {
                    const {nodes} = this.getLastElement();
                    nodes[tag] = nodes[tag] || [];
                    nodes[tag].push(element);
                }
                this.elements.push(element);
            },
            text: (text) => {
                this.getLastElement().text += text.trim();
            },
            endElement: (tag) => {
                const element = this.elements.pop();
                if (this.elements.length === 0) {
                    const path = this.stages.join('/');
                    this.emit(path, element);
                    this.findingState.endElement(tag);
                    this.currentState = this.findingState;
                }
            }
        }

        this.currentState = this.findingState;

        this.parser.on('startElement', (...args) => this.currentState.startElement(...args));
        this.parser.on('endElement', (...args) => this.currentState.endElement(...args));
        this.parser.on('text', (...args) => this.currentState.text(...args));

        this.parser.on('error', (error) => {
        })
    }

    on(eventName, listener) {
        super.on(eventName, listener);
        this.events = this.eventNames();
    }

    getLastElement() {
        return this.elements[this.elements.length - 1];
    }

    _write(chunk, encoding, callback) {
        this.parser.write(chunk);
        callback();
    }
}

const xmlParser = new XMLParser();

xmlParser.on('/root/date', (ctx) => {
     console.log(JSON.stringify(ctx));
});

xmlParser.on('/root/categories/category', (ctx) => {
    //console.log(JSON.stringify(ctx));
});

xmlParser.on('/root/products/product', (ctx) => {
    //console.log(JSON.stringify(ctx));
});

xmlParser.parser.on('startElement', (name, attributes) => {
    if (name === 'root') {
        console.log(attributes['targetNamespace']);
    }
})

const stream = fs.createReadStream('file.xml');
stream.pipe(xmlParser);