title: Casting a FormArray to an array angular
body: <p>I have a FormArray of FormGroups, i want to iterate over the FormArray and detect which FormGroups are valid. However i am unable to do so as i am unable to iterate over a FormArray as it is not of type Array or string. My logic was to somehow cast the FormArray into an Array if possible. However i do not know the syntax in typescript for this. </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
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  <pre class="snippet-code-html lang-html prettyprint-override"><code> this.applicationFormArray = new FormArray([
              this.selectAppFormGroup = new FormGroup({
              }),
              this.generalAppFormGroup = new FormGroup({
              }),
              this.fileModeFormGroup = new FormGroup({
              }),
              this.accessListFormGroup = new FormGroup({
              }),
          ]);</code></pre>
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  </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>checkValidity() {
          var foo = this.applicationFormArray as Array&lt;&gt;;
          for(var element of this.applicationFormArray){
              if(element.valid) {
                  //do something
              }
          }</code></pre>
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  </p>