How can i validate dynamic input in formArray individually?

Issue

when i add two or more dynamic field and i enter input with cpf number the validation happens when i enter cpf in last field, its possible to validate a input field individually?

<h1>Reactive Form Table Example</h1>

<form [formGroup]="form">
    <ng-container formArrayName="cpfs">
          <table class="form-group">
            <tr>
            <    th>cpf</th>
            </tr>
            <ng-container *ngFor="let cpf of cpfs.controls; let i = index;">
            <tbody>
                    <tr [formGroupName]="i">
                       <td>
                            <input type="text" class="form-control" id="cpf" formControlName="cpf" maxlength="11" />
                        </td>
                        <td *ngIf="!isValidCPF('cpf')">
                          CPF é invalido
                        </td>
                        <td>
                            <button (click)="deleteRow(i)" class="btn btn-danger">
                            Delete
                           </button>
                       </td>
                    </tr>
                </tbody>
            </ng-container>
        </table>
        <button type="button" (click)="addCpf()" class="btn btn-dark mt-5">
            Add new Row
        </button>
            <button type="submit" class="btn btn-primary mt-5" 
[disabled]="form.invalid">Submit</button>
        <pre>{{ form?.value | json }}</pre>
        <pre>{{ cpfForm?.value | json }}</pre>
    </ng-container>
</form>

here is a link to the problem, can someone help? https://stackblitz.com/edit/angular-ivy-1d8zur?file=src/app/app.component.ts

Solution

I find solution thanks to someone who helped me, i need to to validate input at index

like code below

code in .ts 

      isValidCPF(index: number) {
        let cpfControl = this.getCpfFormByIndex(index).get('cpf');
        let cpf: String = cpfControl.value;
        if (cpf.length < 11) {
          return false;
        }
        return true;
       }

  getCpfFormByIndex(index: number): FormGroup {
    return this.cpfs.at(index) as FormGroup;
  }

    in html

      <h1>Reactive Form Table Example</h1>

    <form [formGroup]="form">
     <ng-container formArrayName="cpfs">
       <table class="form-group">
          <tr>
            <th>cpf</th>
          </tr>
          <ng-container *ngFor="let cpf of cpfs.controls; let i = index">
            <tbody>
              <tr [formGroupName]="i">
                <td>
                  <input
                  type="text"
                  class="form-control"
                  id="cpf"
                  formControlName="cpf"
                  maxlength="11"
                />
                </td>
                <td
                  *ngIf="!isValidCPF(i) && getCpfFormByIndex(i).get('cpf').dirty"
                  style="color:#FF000F"
                >
                  CPF is invalid!
                </td>
               <td
                 *ngIf="isValidCPF(i) && getCpfFormByIndex(i).get('cpf').dirty"
                  style="color:#176105"
                >
                  CPF is valid
                </td>
                <td>
                  <button (click)="deleteRow(i)" class="btn btn-danger">
                    Delete
                  </button>
                </td>
              </tr>
            </tbody>
          </ng-container>
        </table>
        <button type="button" (click)="addCpf()" class="btn btn-dark mt-5">
          Add new Row
        </button>
        <button
         type="submit"
          class="btn btn-primary mt-5"
          [disabled]="form.invalid"
    >
          Submit
        </button>
        <pre>{{ form?.value | json }} - iSValid {{ form.status | json }}</pre>
        <pre>{{ cpfForm?.value | json }} - iSValid {{ cpfForm.status | json }}</pre>
       </ng-container>
     </form>



    here is live example, add 3 or mor input cpf field and enter some number , it 
    will validate only that input field that are you is typing

  

here is an example how to do that, thank you everbody,

stackblitz: https://stackblitz.com/edit/angular-ivy-1d8zur?file=src/app/app.component.html

Answered By - Marcelo