服务器端

export interface MessageEvent {
data: string | object;
id?: string;
type?: string;
retry?: number;
}

@Sse('voteRecordsCount/:topicId')
voteRecordsCount(@Param('topicId') topicId: string): Observable<MessageEvent> {
return new Observable((ser) => {
  countDocuments({ topicId }).then(r => {
    ser.next({ data: {count:r} })
    ser.complete()
  })
})
}

客户端

const eventSource = new EventSource('voteRecordsCount/xxxx')
eventSource.onmessage = ({ data }) => {
  console.log('New message', JSON.parse(data));
};