Can we declare all variables required in my class in external .ts file?

So I am working on an Ionic app and have a lot of variable declarations inside my class (WelcomeAunthenticatedUser.ts) and those variables are used in my class functions. But I was trying to declare all those vars in an external .ts file and export that file and import it in my class. This is Is there any way to do that?

This is the Variables.ts file which I want to export into my class.

export var Variables: {
    currentUser: string
    scannedCode: string
    currentAccessToken: string
    imageUrl: string
    product: number
    cartCode: number
    productQuantity: 1
    //barcodeDataFields Vars
        barcodeDataFieldsName: string
        barcodeDataFieldsProductCode: string
        barcodeDataFieldsDescription: string
        barcodeDataFieldsImage: string
        barcodeDataFieldsPrice: string

    //productCart Vars
        Quantity: number
        Status: string

    // userCart Vars
        userCartName: string
        userCartCode: number
        userCartProductCode: number
        userCartPrice: number
        userCartTotalPrice: number
        userCartQuantity: number
        userCartEntryNumber: number
        userCartVisibility: boolean

    showButton: boolean
    quantity: number
}

And I am importing it in my Welcome class:

import { Variables } from './../../constants/variables'
import { Paths } from './../../constants/constants'
import { ToastController } from '@ionic/angular';
import { TranslateService } from '@ngx-translate/core';
import { AlertController } from '@ionic/angular';

@Component({
  selector: 'app-welcome-authenticated-user',
  templateUrl: './welcome-authenticated-user.page.html',
  styleUrls: ['./welcome-authenticated-user.page.scss'],
})

export class WelcomeAuthenticatedUserPage implements OnInit {
  productQuantity = 1;
  ngOnInit() {
     Variables.currentUser = this.localStorage.retrieve(LocalStorage.USERNAME);
     Variables.currentAccessToken = this.localStorage.retrieve(LocalStorage.ACCESS_TOKEN);
     Variables.cartCode = this.localStorage.retrieve(LocalStorage.CART_CODE);
     Variables.showButton = false;
  }

And when I run it, it shows an error like this:

Toast Called
core.js:6014 ERROR TypeError: Cannot read property 'cartCode' of undefined
    at WelcomeAuthenticatedUserPage.ionViewWillEnter (welcome-authenticated-user.page.ts:32)
    at HTMLElement.handler (ionic-angular.js:2075)
    at ZoneDelegate.invokeTask (zone-evergreen.js:391)
    at Object.onInvokeTask (core.js:39680)
    at ZoneDelegate.invokeTask (zone-evergreen.js:390)
    at Zone.runTask (zone-evergreen.js:168)
    at ZoneTask.invokeTask [as invoke] (zone-evergreen.js:465)
    at invokeTask (zone-evergreen.js:1603)
    at HTMLElement.globalZoneAwareCallback (zone-evergreen.js:1629)
    at lifecycle (index-157155ee.js:148)

core.js:6014 ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'currentUser' of undefined
TypeError: Cannot read property 'currentUser' of undefined
    at WelcomeAuthenticatedUserPage.<anonymous> (welcome-authenticated-user.page.ts:50)
    at Generator.next (<anonymous>)

Any way I could do this?