easy date validation

date-validation

function isValidDate(value, userFormat) {
// Set default format if format is not provided
userFormat = userFormat || ‘mm/dd/yyyy’;
// Find custom delimiter by excluding
// month, day and year characters
var delimiter = /[^mdy]/.exec(userFormat)[0];
// Create an array with month, day and year
// so we know the format order by index
var theFormat = userFormat.split(delimiter);
// Create array from user date
var theDate = value.split(delimiter);
function isDate(date, format) {
var m, d, y, i = 0, len = format.length, f;
for (i; i < len; i++) {       f = format[i];       if (/m/.test(f)) m = date[i];       if (/d/.test(f)) d = date[i];       if (/y/.test(f)) y = date[i];     }     return (       m > 0 && m < 13 &&       y && y.length === 4 &&       d > 0 &&
// Check if it’s a valid day of the month
d <= (new Date(y, m, 0)).getDate()
);
}
return isDate(theDate, theFormat);
}