这样做，它就会工作

onChildChanged(ref(this.db, '/chats'), (resp) => {
      this.chats = [];
      if( this.iOS() ){
        //IOS
        resp.forEach((element) => {
          console.log('change', element.val());
          const data = element.val();
          const chat: any = {};
          chat.nickname = data["nickname"];
          // chat.date = formatDate(data["date"], 'yyyy-MM-dd hh:mm:ss', 'en-US');
          chat.date = this.iosDate(data["date"]);
          chat.type = data['type'];
          chat.message = data['message'];
          
          this.chats.push(chat);
          this.scroolToEnd();
        }); 
      }else{
        // not IOS
        resp.forEach((element) => {
          console.log('change', element.val());
          const data = element.val();
          const chat: any = {};
          chat.nickname = data["nickname"];
          chat.date = formatDate(data["date"], 'yyyy-MM-dd hh:mm:ss', 'en-US');
          chat.type = data['type'];
          chat.message = data['message'];
          
          this.chats.push(chat);
          this.scroolToEnd();
        });
      }

      
    });

和

get(ref(this.db, `chats/${this.roomname}`)).then((re) => {
      console.log('chatsssss', re.toJSON());
      if( this.iOS() ){
        //IOS
        re.forEach((e) => {
          const childKey = e.key;
          const data = e.val();
          const chat: any = {};
          chat.nickname = data["nickname"];
          // chat.date = formatDate(data["date"], 'yyyy-MM-dd hh:mm:ss', 'en-US');
          chat.date = this.iosDate(data["date"]);
          chat.type = data['type'];
          chat.message = data['message'];
          this.chats.push(chat);
          console.log("childKey", chat);
          this.scroolToEnd();
        });
      }else{
        // notIOS
        re.forEach((e) => {
          const childKey = e.key;
          const data = e.val();
          const chat: any = {};
          chat.nickname = data["nickname"];
          chat.date = formatDate(data["date"], 'yyyy-MM-dd hh:mm:ss', 'en-US');
          chat.type = data['type'];
          chat.message = data['message'];
          this.chats.push(chat);
          console.log("childKey", chat);
          this.scroolToEnd();
        });
      }
      
    });
  }

  iosDate(date:any){
    var dateDays = date.split(" ")[0]
    var day = dateDays.split("-")[2]
    var month = dateDays.split("-")[1]
    var year = dateDays.split("-")[0]
    var dateHours = date.split(" ")[1]
    var hour = dateHours.split(":")[0]
    var minutes = dateHours.split(":")[1]
    var seconds = dateHours.split(":")[2]
    var hoursString = ""
    return `${year}-${month}-${day} ${hour}:${minutes}:${seconds}`
}
   iOS() {
    return [
      'iPad Simulator',
      'iPhone Simulator',
      'iPod Simulator',
      'iPad',
      'iPhone',
      'iPod'
    ].includes(navigator.platform)
    // iPad on iOS 13 detection
    || (navigator.userAgent.includes("Mac") && "ontouchend" in document)
  }