title: Angular - FormArray, how to reset a specific field of a formArray?
body: <p>I can't figure out how to reset a single field of a FormArray, for example:</p>
  
  <pre><code>myForm = this.fb.group(
          {
              title: ["", [Validators.required, Validators.minLength(4)]],
              date: ["", Validators.required],
              pairs: this.fb.array(
                  this.fPairs.map(f =&gt;
                      this.fb.group({
                          score: [],
                          value: [],
                          valueRel: []
                      })
                  )
              )
          },
          {
              validator: minMaxValidator
          }
      );
  </code></pre>
  
  <p>so my FormArray is an Array of 4 Objects as it's mapped from:</p>
  
  <pre><code>fPairs: Array&lt;fPairs&gt; = [
          {score: 0, value: 0, valueRel: 0},
          {score: 0, value: 0, valueRel: 0},
          {score: 0, value: 0, valueRel: 0},
          {score: 0, value: 0, valueRel: 0}
      ];
  </code></pre>
  
  <p>what I achieved so far, to reset this part of my form, is:</p>
  
  <pre><code>pairsControl= this.myForm.controls["pairs"] as FormArray;
  </code></pre>
  
  <p>and then use:</p>
  
  <p>this.pairsControl.reset();</p>
  
  <p>but this resets EVERY field of the FormArray, and what I want instead, is being able to reset only a specific field,</p>
  
  <p>for example the "<code>score"</code> field of all 4 objects, while leaving intact the value and the valueRel fields</p>
  
  <p>I tried this:</p>
  
  <pre><code>this.fixedPointsControl.reset(["score"]);
  </code></pre>
  
  <p>but what it does, is reset everything like the previous expression, so nothing changes!</p>
  
  <p>What s the correct way to reset a specific field of a formArray?</p>