dynamically set the date value in matdatepicker field affect the another matDatePicker field Date in Reactive Form

Question

I have two matDatePicker control (statement date and start date) in my reative form I have dynamically set the value of start date field based on statement date field value and number of month.

<div [formGroup]="parameters">
<div class="mat-field">
    <mat-form-field color="primary">
        <mat-label>Statement Date</mat-label>
        <input id="statementDate" matInput [matDatepicker]="statementDatePicker"  formControlName="statementDate"  (dateChange)="datechanged()" >
        <mat-datepicker-toggle matSuffix [for]="statementDatePicker"></mat-datepicker-toggle>
        <mat-datepicker #statementDatePicker></mat-datepicker>
    </mat-form-field>
</div>
<div class="mat-field">
    <mat-form-field>
        <mat-label>Start Date</mat-label>
        <input id="startDate" matInput [matDatepicker]="startDatepicker" formControlName="startDate" readonly [disabled]="parameters.value.period!='other'">
        <mat-datepicker-toggle matSuffix [for]="startDatepicker"></mat-datepicker-toggle>
        <mat-datepicker #startDatepicker></mat-datepicker>
    </mat-form-field>
</div>
<div class="mat-field">

    <mat-form-field>
        <mat-label>Period</mat-label>
        <mat-select id="period" matInput formControlName="period" (selectionChange)="datechanged()">
            <mat-option value="12">12 Months</mat-option>
            <mat-option value="11">11 Months</mat-option>
            <mat-option value="10">10 Months</mat-option>
            <mat-option value="9">9 Months</mat-option>
            <mat-option value="8">8 Months</mat-option>
            <mat-option value="7">7 Months</mat-option>
            <mat-option value="6">6 Months</mat-option>
            <mat-option value="5">5 Months</mat-option>
            <mat-option value="4">4 Months</mat-option>
            <mat-option value="3">3 Months</mat-option>
            <mat-option value="2">2 Months</mat-option>
            <mat-option value="1">1 Month</mat-option>
            <mat-option value="other">other</mat-option>
        </mat-select>
    </mat-form-field>
</div>

ts file

 export class DatepickerMinMaxExample {
 parameters: FormGroup

  constructor(
    private fb: FormBuilder
  ) { }

  ngOnInit() {
   this.parameters = new FormGroup({
      'statementDate': new FormControl(null, Validators.required),
      'startDate': new FormControl(null, Validators.required),
      'period': new FormControl(null, Validators.required),
  });

  }
    
 public datechanged(){
    if(this.parameters.controls['statementDate'].value!=null&& this.parameters.controls['period'].value!=null&& this.parameters.controls['period'].value!='other'){
      let stmtDate=this.parameters.controls['statementDate'].value;
      let send_date=this.parameters.controls['statementDate'].value;
      console.log('statement date: '+ this.parameters.controls['statementDate'].value)
      let period=parseInt(this.parameters.controls['period'].value)
      let formattedDate : any;
   
      send_date.setMonth(send_date.getMonth()-period);
      send_date.setDate(send_date.getDate()+1);
      formattedDate=send_date.toISOString().slice(0,10);
      console.log('format date: '+ formattedDate)
      console.log('stment date after format date: '+ stmtDate)
      this.parameters.controls['startDate'].setValue(new Date(formattedDate))
    }

}
}

dynamically updating the start date value affect the statement date matDatePicker and value as well.

Stackblitz

Please help me to resolve this issue.

Thanks in advance.

Answer 1

public datechanged(){
    if(this.parameters.controls['statementDate'].value!=null&& this.parameters.controls['period'].value!=null&& this.parameters.controls['period'].value!='other'){
      this.parameters.controls['startDate'].setValue(new Date(this.parameters.controls['statementDate'].value))
      let startDate=this.parameters.controls['startDate'].value
      let period=parseInt(this.parameters.controls['period'].value)
      let formattedDate : any;
   
      startDate.setMonth(startDate.getMonth()-period);
      startDate.setDate(startDate.getDate()+1);
      formattedDate=startDate.toISOString().slice(0,10);
      this.parameters.controls['startDate'].setValue(new Date(formattedDate))
    }

}