HarmonyOS 为什么HashMap被Json转换后只剩下：{}

map转json的方法示例参考如下：

function mapToString(map: Map<string, string | number | object>): string {
  if (map.size === 0) {
    return '';
  }
  let obj: object = new Object;
  map.forEach((value, key) => {
    obj[key] = value;
  })
  return JSON.stringify(obj);
}

function mapToObj(map: Map<string, string | number | object>): object {
  if (map.size === 0) {
    return [];
  }
  let obj: object = new Object;
  map.forEach((value, key) => {
    obj[key] = value;
  })
  return obj;
}

let map = new Map<string, string>()
map.set('machineModel', 'xxx')
map.set('deviceToken', '')
map.set('deviceType', '1')
map.set('src', '00')
map.set('deviceSdk', '1003')
map.set('appVersion', '1.0.0')
map.set('deviceEnv', '0')
map.set('sdkVersion', '1.0.0')
let str = mapToObj(map)
console.debug('str:'+ JSON.stringify(str))
let map1 = new Map<string, string>()
map1.set('machineModel', 'A111111')
map1.set('deviceToken', '22222')
map1.set('deviceType', '222221')
map1.set('src', '001111')
map1.set('deviceSdk', '444455')
map1.set('appVersion', '1111.0.0')
map1.set('deviceEnv', '0111')
map1.set('sdkVersion', '1111.0.0')
let str1 = mapToObj(map1)
let arr:Array<object> = [str,str1]
let resMap = new Map<string, object[]>()
resMap.set('headBean',arr)
let  reStr = mapToString(resMap)
console.debug('resMapstr:'+ reStr)