Date and Currency validation in Angular (4)

Question

I am new to Angular. I am using angular 4 reactive forms and figured out how to perform custom validations. Following is my implementation for numeric

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Answer 1

Created a custom validator to handle formats MM/DD/YYYY and MMDDYYYY

function dateValidator(c: AbstractControl): { [key: string]: boolean } | null {
    if (c.pristine) {
        return null;
    }
    if ((c.value !== undefined && c.value !== '' && c.value != null)) {

        var month = null;
        var day = null;
        var year = null;
        var currentTaxYear = Number(new Date().getFullYear() - 1);
        if (c.value.indexOf('/') > -1) {
            var res = c.value.split("/");           
            if (res.length > 1) {
                month = res[0];
                day = res[1]
                year = res[2];
            }                              
        }
        else {
            if (c.value.length == 8) {
                month = c.value.substring(0, 2);
                day = c.value.substring(2, 4);
                year = c.value.substring(4, 8);
            }            
        }
        if (isNaN(month) || isNaN(day) || isNaN(year)) {
            return { 'dateInvalid': true };
        } 
        month = Number(month);
        day = Number(day);
        year = Number(year);
        if (month < 1 || month > 12) { // check month range
            return { 'dateInvalid': true };
        }
        if (day < 1 || day > 31) {
            return { 'dateInvalid': true };
        }
        if ((month === 4 || month === 6 || month === 9 || month === 11) && day === 31) {
            return { 'dateInvalid': true };
        }
        if (month == 2) { // check for february 29th
            var isleap = (year % 4 === 0 && (year % 100 !== 0 || year % 400 === 0));
            if (day > 29 || (day === 29 && !isleap)) {
                return { 'dateInvalid': true };
            }
        }
        if (year !== currentTaxYear) {
            return { 'dateYearGreaterThanTaxYear': true };
        }
    }
    return null;
}