Angular - iterate formArray

https://stackoverflow.com/questions/49395203/iterate-angular-2-formarray

formArray {

controls:[....formControl1,fomrControl2...]

} 

for (let control of formArray.controls) {

   if (control instanceof FormControl) {
      // is a FormControl
   }
   if (control instanceof FormGroup) {
      // is a FormGroup  
   }
   if (control instanceof FormArray) {
      // is a FormArray
   }