HarmonyOS 获取时间戳

使用systemDateTime.getTime(),可以参考文档：

https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/js-apis-date-time-V5#systemdatetimegettime10

示例如下:

aboutToAppear(): void {
  try {
  let time = systemDateTime.getTime(true)
  console.log(JSON.stringify(time))
} catch(e) {
  let error = e as BusinessError;
  console.info(`Failed to get time. message: ${error.message}, code: ${error.code}`);
}
}