How to show only one item in Angular2, Ionic2 - node.js

Question

Please bear with my question as I'm new to Angular and I don't know exactly where the problem is, I've tried to google for a solution but with no good luck, basically I'm running a simple NodeJS server with socket.io:
SERVER
var socket = require('socket.io'),
http = require('http'),
server = http.createServer(),
socket = socket.listen(server);
var msgProva = 2;
socket.on('connection', function(connection) {
console.log('User Connected');
socket.emit('prova', msgProva);
connection.on('message', function(msg){
socket.emit('message', msg);
});
connection.on('sValue', function(value){
console.log('sValue', value );
socket.emit('sValue', value);
});
});
server.listen(3000, function(){
console.log('Server started');
});
and my client TS code:
HOME.TS
import { Component } from '#angular/core';
import { NavController } from 'ionic-angular';
import * as io from 'socket.io-client';
#Component({
selector: 'page-home',
templateUrl: 'home.html'
})
export class HomePage {
socket:any
chat_input:string;
chats = [];
prova = [];
slideValueBadge = [];
constructor(public navCtrl: NavController) {
var a;
this.socket = io('http://localhost:3000');
this.socket.on('message', (msg) => {
console.log("message", msg);
this.chats.push(msg);
});
this.socket.on('prova', (msgProva) => {
console.log("msgProva", msgProva);
this.prova.push(msgProva);
});
this.socket.on('sValue', (value) => {
let index: number = this.slideValueBadge.indexOf(value);
if (index != -1) {
a = this.slideValueBadge.splice(index, 1);
}
console.log("sliderValue:", value);
});
}
send(msg) {
if(msg != ''){
this.socket.emit('message', msg);
}
this.chat_input = '';
}
cValue(event, nome) {
console.log("SliderValue", event._valA);
this.socket.emit('sValue', event._valA);
}
}
HOME.HTML
<ion-content padding>
<ion-item>
<ion-range [(ngModel)]="brightness" (ionChange)="cValue($event, 'slider1')">
<ion-icon range-left small name="water"></ion-icon>
<ion-icon range-right name="water"></ion-icon>
</ion-range>
</ion-item>
Flusso d'acqua
<ion-badge color="secondary">{{slideValueBadge}}</ion-badge>
<ion-list>
<ion-item *ngFor="let message of chats">{{message}}</ion-item>
</ion-list>
<ion-item>
<ion-input type="text" [(ngModel)]="chat_input" placeholder="Enter message"></ion-input>
</ion-item>
<button ion-button block (click)="send(chat_input)">Send</button>
</ion-content>
And that is what I see as result:
How can I display only one value? (the last one)?

Answer 1

Basically you are binding your badge to an array (slideValueBadge = []).
Simply change the binded value to a number and then update it in your socket.on method.
Hope this could help you

Answer 2

Apparently this was the solution, dunno if is good or bad coding:
<ion-badge color="secondary">{{slideValueBadge[slideValueBadge.length -1]}}</ion-badge>
without the *ng-if