Артем

var positions = ['Яблоко','Груша','Апельсин','Банан'];
    positions.forEach( function (fruit, index) {
      // Start from index 0
      fruit =  index +' '+ fruit;

      // Start from index 1
      fruit =  ( index + 1 ) +' '+ fruit;
    });

console.log(positions[0]) // 0 - Яблоко
console.log(positions[0]) // 1 - Яблоко

<form [formGroup]="loginForm" (ngSubmit)="onSubmitLoginForm()" novalidate>
   <input formControlName="userLogin" #userLoginInput type="email">
   <input formControlName="userPassword" type="password">
</form>

// import 
import { FormBuilder, FormGroup, Validators } from "@angular/forms";

export class AuthorizationFormComponent {

  public loginForm : FormGroup;

  @ViewChild('userLoginInput') userLoginInput;

  constructor(
    private _builder : FormBuilder,
  ) {
    // Form builder and validation configuration
    this.loginForm = this._builder.group({
      userLogin: [ '', [ Validators.required ] ],
      userPassword: [ '', [ Validators.required ] ],
    });
  }

  onSubmitLoginForm () {
    this.userLoginInput.nativeElement.focus()
  }
}

<app-for-example *ngFor="let item of dataCell" [dataCell]="dataCell" [ngSwitch]="item. type">
  <path *ngSwitchCase ="item.type == 'path'" attr.fill="{{item.fill}} attr.id="{{item.id}}></path>
  <polyline *ngSwitchCase ="item.type == 'polyline'" attr.fill="{{item.fill}} attr.id="{{item.id}}></polyline>
</app-for-example>