Javascript to compare two dates, from strings, begin <= end

Question

I get two strings formated like (Brazilian Format): "DD/MM/YYYY", I need to compare both. Since the first field is the begin and the last is the end,

My validation is begin <= end

Date.new(begin) is generating 'invalid date' even on ISO !

Answer 1

Don't use Date.new. Use new Date(). Because of the format of your date string, I would recommend grabbing each field individually and passing them into the constructor:

var startYear = parseInt(document.getElementById('startYear'), 10);
var startMonth = parseInt(document.getElementById('startMonth'), 10) - 1; // as per Residuum's comment
var startDay = parseInt(document.getElementById('startDay'), 10);
var start = new Date(startYear, startMonth, startDay);

etc. If you're handed a date string, then you can use fuzzy lollipop's method to get each field from the string. I'm not sure if the Date constructor will accept unparsed strings for the individual fields, however.

The, once you have the two dates you'd like to compare, just compare their values in milliseconds since the epoch:

function isValid(start, end) {
    return start.getTime() < end.getTime();
}