xml.helper.js

function xml() {

    return {
        toJSONObject: function(xml) {
            return (xml ? toJSON(xml) : xml);
        },

        fromJSONObject: function(json) {
            return this.fromString(toXML(json));
        },

        toString: function(obj) {
            return (obj ? (new XMLSerializer()).serializeToString(obj.nodeType === undefined ? this.fromJSONObject(obj) : obj) : '');
        },

        fromString: function(str) {
            return (str.charAt(0) == '<' ? (new DOMParser()).parseFromString(str.trim(), 'text/xml') : toXML(window.JSON.parse(str)));
        }
    };

    function toJSON(xml) {
        let obj = {};
        let attr;

        // object type
        if (xml.nodeType == 1) { // element
            if (xml.attributes && (xml.attributes.length > 0)) {
                obj['#attributes'] = {};
                for (let i = 0; i < xml.attributes.length; i++) {
                    attr = xml.attributes.item(i);
                    obj['#attributes'][attr.nodeName] = attr.nodeValue;
                }
            }
        } else if (xml.nodeType == 3) // text
            obj = xml.nodeValue;

        // do children
        if (xml.hasChildNodes()) {
            for (let i = 0; i < xml.childNodes.length; i++) {
                let vItem = xml.childNodes.item(i),
                    vNodeName = vItem.nodeName;
                if (typeof(obj[vNodeName]) == 'undefined') obj[vNodeName] = toJSON(vItem);
                else {
                    if (typeof(obj[vNodeName].length) == 'undefined') {
                        let vOld = obj[vNodeName];
                        obj[vNodeName] = [];
                        obj[vNodeName].push(vOld);
                    }
                    obj[vNodeName].push(toJSON(vItem));
                }
            }
        }
        return obj;
    }

    function toXML(json, pTagName) {
        const vAttrList = [];

        let attrs = {};
        let vInnerXML = '';

        if (attrs = json['#attributes'])
            for (let attr in attrs)
                vAttrList.push(attr + '="' + attrs[attr] + '"');

        if (!(vInnerXML = json['#text'])) {
            let vInnerList = [];
            for (let vPrp in json)
                if (vPrp.charAt(0) != '#')
                    vInnerList.push(toXML(json[vPrp], vPrp));

            vInnerXML = vInnerList.join('\r\n');
        }

        if (pTagName)
            return '<' + pTagName + ' ' + vAttrList.join(' ') + '>' + vInnerXML + '</' + pTagName + '>';
        else
            return vInnerXML;
    }
}