resuable validator for multiple cases - validation

Question

I made a date validator. It validates existing dates. I need multiple date validator with other restrictions, for ex : a max date validator that won't let the user put in a future date or a date validator that only takes past dates. This is my current validator.
export function dateValidator(group) {
const {day, month, year} = group.value;
const fullDate = `${day}/${month}/${year}`;
const dobPattern = /^(\d{1,2})[-\/](\d{1,2})[-\/](\d{4})$/;
const isStringValid = dobPattern.test(fullDate);
let isValid = false;
if (isStringValid) {
const intDay = Number(day);
const intMonth = Number(month);
const intYear = Number(year);
const jsMonth = intMonth - 1;
const date = new Date(intYear, jsMonth, intDay);
isValid = (date.getFullYear() === intYear && date.getMonth() === jsMonth && date.getDate() === intDay ;
}
return isValid ? null : { invalid: 'Invalid date' };
};
How can I restrict the user from putting in future dates.
I used this code with the following line:
isValid = (date.getFullYear() === intYear && date.getMonth() === jsMonth && date.getDate() === intDay ;
But I wonder if there is an easier way without having to copy and past this code over and over again to make small restrictions to it.

Answer 1

Your dateValidator() function should be a function factory (i.e. a function that returns a function) instead of a function that returns the error directly:
export function dateValidator(maxDate: string): ValidatorFn {
// Return a validator function.
return (group: FormGroup): {[key: string]: any} => {
// Re-use your existing validation code here and return the error if any.
// Optionally, use the `maxDate` param to customize the validation:
// entered dates should not go beyond `maxDate`.
};
}
As you can see, you can customize the validator function by passing parameters to the function factory. In my example, I used a maxDate parameter to indicate the furthest date in time that the validator should allow.
In your form model, use this validator by calling the factory with the appropriate value, e.g. :
this.myForm = fb.group({
'date': ['', [Validators.required(), dateValidator('02/20/2017')]]
});
You can see another example of a function factory for a validator in the doc: https://angular.io/docs/ts/latest/cookbook/form-validation.html#custom-validation