此功能对我来说效果很好：

xmlToJson = function(xml) {
    var obj = {};
    if (xml.nodeType == 1) {                
        if (xml.attributes.length > 0) {
            obj["@attributes"] = {};
            for (var j = 0; j < xml.attributes.length; j++) {
                var attribute = xml.attributes.item(j);
                obj["@attributes"][attribute.nodeName] = attribute.nodeValue;
            }
        }
    } else if (xml.nodeType == 3) { 
        obj = xml.nodeValue;
    }            
    if (xml.hasChildNodes()) {
        for (var i = 0; i < xml.childNodes.length; i++) {
            var item = xml.childNodes.item(i);
            var nodeName = item.nodeName;
            if (typeof (obj[nodeName]) == "undefined") {
                obj[nodeName] = xmlToJson(item);
            } else {
                if (typeof (obj[nodeName].push) == "undefined") {
                    var old = obj[nodeName];
                    obj[nodeName] = [];
                    obj[nodeName].push(old);
                }
                obj[nodeName].push(xmlToJson(item));
            }
        }
    }
    return obj;
}

实现方式：

var jsonText = JSON.stringify(xmlToJson(xmlDoc)); // xmlDoc = xml dom document