There an easier way? RXJS subject to increment likes on an array object

likes.rxjs.ts.js

// this really what it takes to increment a counter on an item in my observable
// likes is a subject, broadcasting the updated array eventually to the source observable being rendered
this.likes
  .map(
    (message: Message): IMessagesOperation =>
      (messages: Message[]) => {
        return messages.map((m: Message) => {
          // todo: check if user has already liked
          if (m.id == message.id) 
            ++m.likes
          return m
        })
      }
  )
  .subscribe(this.updates)

// help me find a better way please =)

Did you think about using .reduce() operator?