JavaScript to validate date

Question

Below is the function to validate date. The should be between Today - 15 and Today. Can some one refactor this code.

phpdatetoday is a

Answer 1

function validate(phpdatetoday, withinDays) {
    var inputDateInMillis = Date.parse(phpdatetoday)

    if (isNaN(inputDate) || isNaN(withinDays)) {
        //handle error
        return;
    }

    var todayInMillis = (new Date()).setHours(0,0,0,0);
    return todayInMillis - inputDateInMillis < (withinDays * 86400000 /*1000ms*60s*60m*24h*/);
}

Date.setHours() will set the hours/minutes/seconds to zero and return milliseconds since 1 Jan 1970 UTC.

Date.parse() will return the parsed date otherwise if it cannot do it then it will return NaN. You can use isNan() to determine whether a variable's value is a number or not. If 'inputDate' is NaN then you can alert the user that the input date was invalid.