JSON.Stringyfy not working

Good day)
I posted a lot of triggers in the page.
And made a array names kto for them values.
But then a made JSON.stringyfy(this.kto) fo sending array in json format i get a empty string
Why?

Page code:

> <ion-content>
>           <ion-item>
>             <ion-label><strong>Пристенки</strong></ion-label>
>           </ion-item>
>           <ion-item>
>             <ion-label>Горят все лампы освещения</ion-label>
>             <ion-toggle [(ngModel)]="this.kto['pr0']"></ion-toggle>
>           </ion-item>
>           <ion-item>
>             <ion-label>Ночные шторки на месте и в рабочем состоянии</ion-label>
>             <ion-toggle [(ngModel)]="this.kto['pr1']"></ion-toggle>
>           </ion-item>
>           <ion-item>
>             <ion-label>Стеклянные дверки (если есть) закрываются и не требуют регулировки</ion-label>
>             <ion-toggle [(ngModel)]="this.kto['pr2']"></ion-toggle>
>           </ion-item>
>           <ion-item>
>             <ion-label>Дренажные сливы чистые</ion-label>
>             <ion-toggle [(ngModel)]="this.kto['pr3']"></ion-toggle>
>           </ion-item>
>           <ion-item>
>             <ion-label>Верхние соты чистые</ion-label>
>             <ion-toggle [(ngModel)]="this.kto['pr4']"></ion-toggle>
>           </ion-item>
>           <ion-item>
>             <ion-label>Обдув свободный, вентиляторы в работе</ion-label>
>             <ion-toggle [(ngModel)]="this.kto['pr5']"></ion-toggle>
>           </ion-item>
>           <ion-item>
>             <ion-label>Температура соответствует уставке контроллера и типу хранимого продукта</ion-label>
>             <ion-toggle [(ngModel)]="this.kto['pr6']"></ion-toggle>
>           </ion-item>  
> 
>           ...    
>           
>           <ion-item>
>             <ion-label><strong>Лари для хранения заморозки и охлажденки</strong></ion-label>
>           </ion-item>
> 
> 
>           <ion-item>
>             <button color="secondary" ion-button block type="button" (click)="Check()">Check</button>    
>           </ion-item>
> </ion-content>

.ts file code:

import { Component } from '@angular/core';
import { NavController, NavParams } from 'ionic-angular';

@Component({
  selector: 'page-add',
  templateUrl: 'add.html',
})
export class AddPage {

  kto: Array<string> = [];

  constructor(
    public navCtrl: NavController, 
    public navParams: NavParams,
  ) {
    
    this.kto['pr0'] = 'false'; this.kto['pr1'] = false; this.kto['pr2'] = false; this.kto['pr3'] = false; this.kto['pr4'] = false; this.kto['pr5'] = false; this.kto['pr6'] = false; this.kto['pr7'] = false; 
    this.kto['lr0'] = false; this.kto['lr1'] = false; this.kto['lr2'] = false; this.kto['lr3'] = false;
    this.kto['chm0'] = false; this.kto['chm1'] = false; this.kto['chm2'] = false; this.kto['chm3'] = false; 
    this.kto['condens0'] = false; this.kto['condens1'] = false; this.kto['condens2'] = false; 
    this.kto['vent0'] = false; this.kto['vent1'] = false; this.kto['vent2'] = false; this.kto['vent3'] = false; this.kto['vent4'] = false; 
    this.kto['cond0'] = false; this.kto['cond1'] = false; this.kto['cond2'] = false; this.kto['cond3'] = false; 
    this.kto['tz0'] = false; this.kto['tz1'] = false; this.kto['tz2'] = false; this.kto['tz3'] = false; 
    this.kto['press0'] = false; this.kto['press1'] = false; this.kto['press2'] = false; 
    this.kto['ad0'] = false; this.kto['ad1'] = false; this.kto['ad2'] = false; 
    this.kto['pm0'] = false; this.kto['pm1'] = false; this.kto['pm2'] = false; this.kto['pm3'] = false; this.kto['pm4'] = false; 
    this.kto['cam0'] = false; this.kto['cam1'] = false; this.kto['cam2'] = false; this.kto['cam3'] = false; this.kto['cam4'] = false; this.kto['cam5'] = false; 

  }

  Check() {
    console.log(JSON.stringify(this.kto));
  }   

}

JSON.Stringyfy?
Maybe, this correctly write is JSON.stringify().
Try console.log(JSON.stringify(this.kto));

Sorry, I make a error then posting sample code.
I use a JSON.stringify and it’s not working((
In console a see only

Use first index, try this:

this.kto['pr0'] = false; 
        this.kto['pr1'] = false; 
        this.kto['pr2'] = false; 
        this.kto['pr3'] = false; 
        this.kto['pr4'] = false; 
        this.kto['pr5'] = false; 
        this.kto['pr6'] = false; 
        this.kto['pr7'] = false;
        this.kto['lr0'] = false; 
        this.kto['lr1'] = false; 
        this.kto['lr2'] = false; 
        this.kto['lr3'] = false;
        this.kto['chm0'] = false; 
        this.kto['chm1'] = false; 
        this.kto['chm2'] = false; 
        this.kto['chm3'] = false;
        this.kto['condens0'] = false; 
        this.kto['condens1'] = false; 
        this.kto['condens2'] = false;
        this.kto['vent0'] = false; 
        this.kto['vent1'] = false; 
        this.kto['vent2'] = false; 
        this.kto['vent3'] = false; 
        this.kto['vent4'] = false;
        this.kto['cond0'] = false; 
        this.kto['cond1'] = false; 
        this.kto['cond2'] = false; 
        this.kto['cond3'] = false;
        this.kto['tz0'] = false; 
        this.kto['tz1'] = false; 
        this.kto['tz2'] = false; 
        this.kto['tz3'] = false;
        this.kto['press0'] = false; 
        this.kto['press1'] = false; 
        this.kto['press2'] = false;
        this.kto['ad0'] = false; 
        this.kto['ad1'] = false; 
        this.kto['ad2'] = false;
        this.kto['pm0'] = false; 
        this.kto['pm1'] = false; 
        this.kto['pm2'] = false; 
        this.kto['pm3'] = false;
        this.kto['pm4'] = false;
        this.kto['cam0'] = false; 
        this.kto['cam1'] = false; 
        this.kto['cam2'] = false; 
        this.kto['cam3'] = false; 
        this.kto['cam4'] = false; 
        this.kto['cam5'] = false;

        console.log(JSON.stringify(this.kto['pr1']));

result: false

did you validated JSON data before using JSON.Stringyfy()? if not, please use these tools which can help to do that.

I thought that JSON.stringify converts an array to json data. How else can you turn an ordinary array into a json array?