Angular 2 form validations start date <= end date

Question

I\'m trying to add validations such that the end date can\'t be before the start date. Unfortunately I have no idea how to do that, and I didn\'t find any helpful advice in

Answer 1

create a form group . Let the controls be a part of form group .

       new FormGroup({   
        startDate: this.fb.group({
            dateInput: [{value: ""}, startDateValidator()]
        }),   
        endDate: this.fb.group({
            dateInput: ["", endDateValidator()]
        })  
    }, startDateCannotBeLessThanEndDateValidator());   

        startDateCannotBeLessThanEndDateValidator(formGroup: FormGroup) {

             let startDate = formGroup.get("startDate");   
            let endDate = formGroup.get("endDate");
            // compare 2 dates 
        }