var szInfo = "<SnapPolygonList><SnapPolygon><id>1</id><polygonType>1</polygonType><color><r>0</r><g>255</g><b>0</b></color><tips>#1#</tips><isClosed>true</isClosed><pointList><point><x>0.272575</x><y>0.738676</y></point><point><x>0.538462</x><y>0.733450</y></point><point><x>0.576923</x><y>0.939024</y></point><point><x>0.319398</x><y>0.958188</y></point><point><x>0.316054</x><y>0.951219</y></point></pointList></SnapPolygon><SnapPolygon><id>2</id><polygonType>1</polygonType><color><r>0</r><g>255</g><b>0</b></color><tips>#2#</tips><isClosed>true</isClosed><pointList><point><x>0.280936</x><y>0.439024</y></point><point><x>0.720736</x><y>0.512195</y></point><point><x>0.239130</x><y>0.634146</y></point><point><x>0.137124</x><y>0.554007</y></point></pointList></SnapPolygon></SnapPolygonList>"

var eventparameter = { "事件参数": {
        "布防区域": [
            {
                "区域坐标": [
                    [0.2001, 0.2001],
                    [0.5002, 0.2002],
                    [0.5003, 0.5003],
                    [0.2004, 0.5004]

                ],
                "区域编号": 1
            }
        ],
        "开始检测时间": "00:00:00",
        "撤防区域": [
            {
                "区域坐标": [
                    [
                        0.24861111111111112,
                        0.27256944444444442
                    ],
                    [
                        0.65555555555555556,
                        0.22395833333333334
                    ],
                    [
                        0.56805555555555554,
                        0.55208333333333337
                    ],
                    [
                        0.40138888888888891,
                        0.68055555555555558
                    ]
                ],
                "区域编号": 1
            }
        ]
        }  
}

var demo = {
    
    "事件参数": {
        "布防区域": [
            {
                "区域坐标": [
                    point

                ],
                "区域编号": id
            }
        ],
        "开始检测时间": "00:00:00",
        "撤防区域": [
            {
                "区域坐标": [
                   point
                ],
                "区域编号": id
            }
        ]
        }
};

用第三方库，xml2json。将xml转为json对象，然后取你想要的信息

var parser = require('xml2json');

// xml to json
var json = parser.toJson(xml);
console.log("to json -> %s", json);