Answers for "valuechanges angular"

angular input onchange

<input (change)="saverange()"/>

angular onChange onChanges SimpleChanges

export class MyClassName implements OnInit,OnChanges {
 @Input() documents: Document[] = [];
.....
ngOnChanges(changes: SimpleChanges){
    console.log("changes ", changes)
    if(changes.documents){
      console.log("changes2 ", changes)
    }
  }

angular 9 form value changes

 
this.reactiveForm.get("firstname").valueChanges.subscribe(selectedValue => {
  console.log('firstname value changed')
  console.log(selectedValue)                              //latest value of firstname
  console.log(this.reactiveForm.get("firstname").value)   //latest value of firstname
})
 

angular formgroup on value change

this.reactiveForm.get("firstname").valueChanges.subscribe(x => {
   console.log('firstname value changed')
   console.log(x)
})