Javascript Valid Date Checking does not work in IE8 (and Firefox)

Question

I have tried two popular answers from Detecting an "invalid date" Date instance in JavaScript for checking valid dates. I tested both of them in IE8 – Unfortunately both are disappointing. See it here http://jsfiddle.net/Lijo/uzSU6/2/

Is there a better JavaScript code that will work in IE8 + Chrome + Firefox?

Note: To my surprise, it doesn't work well in Firefox too...

CONDITION

The date format is expected to be US date format with slashes (/)

CODE

isValidDateCheck2('12/33/2012') ;
isValidDateCheck1('12/12/2012') ;

function isValidDateCheck1(d) 
{
  alert(Object.prototype.toString.call(d));
  if ( Object.prototype.toString.call(d) !== "[object Date]" )
  {
    alert('Not Valid');
  }
  if(!isNaN(d.getTime()))
  {
  alert(d.getTime());
  }
  }

  function  isValidDateCheck2(d)
  {    
    var timestamp=Date.parse(d);
    alert(timestamp);

    if (isNaN(timestamp)==false)
    {
        var date=new Date(timestamp);
        alert(date);                    
    }
   }

EDIT

@mplungjan approach (first suggested) is listed in http://jsfiddle.net/Lijo/uzSU6/7/. This was failed in IE8 for one scenario - http://jsfiddle.net/Lijo/uzSU6/12/.

Answer 1

You seem to be conflating two things here. Valid date objects and valid dates. These are not the same problem.

The question you linked to answers how to test for validity of date objects (whether a date object is an "invalid date" instance). Invalid date objects are generated when you use invalid parameters when constructing them: new Date('?')

What you want is to test if a date string conforms to a predefined date format. This is an entirely different problem that should not be solved by using only date objects.

Generally speaking, there are a couple of reasons for this; the first is that the browsers will helpfully compute overflow months/days/time to the correct date: new Date(2012,0,290) === Oct 06 2012.

Secondly because the parser may be locale dependent (mm/dd vs. dd/mm?). When the date is parsed by the browser my locale may cause it roll it to my timezone/DST thus skewing it and messing up detection (.getDate may now return next day over). Even worse, this may only occur across some timezones at certain parts of the year.

I strongly encourage using a library like date.js to handle this stuff because dates are much harder than you think! If you absolutely must validate by hand, then I recommend doing it in detail like this:

function isValidDate (str) {
  // parse to numbers
  const rm = str.split('/');
  const m = 1 * rm[0];
  const d = 1 * rm[1];
  const y = 1 * rm[2];
  if (isNaN(m * d * y)) {
    return false;
  }
  // day can't be 0
  if (d < 1) {
    return false;
  }
  // month must be 1-12
  if (m < 1 || m > 12) {
    return false;
  }
  // february
  if (m === 2) {
    const isLeapYear = ((y % 4 === 0) && (y % 100 !== 0)) || (y % 400 === 0);
    // leap year
    if (isLeapYear && d > 29) {
      return false;
    }
    // non-leap year
    if (!isLeapYear && d > 28) {
      return false;
    }
  }
  // test any other month
  else if (
    ((m === 4 || m === 6 || m === 9 || m === 11) && d > 30) ||
    ((m === 1 || m === 3 || m === 5 || m === 7 || m === 8 || m === 10 || m === 12) && d > 31)) {
    return false;
  }
  return true;
}

As a jsFiddle: http://jsfiddle.net/3pMPp/1/
As a jsPerf: http://jsperf.com/silly-date-valiation

Answer 2

This will handle actual dates and give you the chance to find what part of the date was invalid - using the DATE OBJECT

NOTE: several browsers will happily parse what seems to be an invalid date and make a date object out of it. For example 02/29/2013 will parse as 1st of March 2013, hence my test to see if the parts entered made sense when used in an actual date.

DEMO

Tested in

Win7:

• Chrome 23 (only one to give isNaN on the first date)
• IE 9

Win XP:

• FX 17
• IE 8
• Safari 5
• Opera 11 and 12

function isValidDateCheck(dString) {

    // test it is nn/nn/nnnn or nn/nn/nn
    var dRe = /^(\d{1,2})([\-\/])(\d{1,2})\2(\d{4}|\d{2})$/

    if (!dRe.exec(dString)) {
      return false; 
    }   

    // make sure it parses as date 
    // replace this part if you do not allow dashes        
    dString.replace(/-/g,"/"); 

    var date = new Date(dString); // create a date object
    if (!isNaN(date)) { // it may give NaN - if not test the parts
        var parts = dString.split("/"); // split on slash
        var dd = parseInt(parts[1],10); // day number
        var mm = parseInt(parts[0],10)-1; // month - JS months start at 0
        var yyyy = parseInt(parts[2],10); // year
        // return true if all parts match
        return dd===date.getDate() && mm === date.getMonth() && yyyy===date.getFullYear();
    }
    // here the date was not parsed as a date
    return false;
}


window.onload=function() {
  document.getElementById("output").innerHTML+="<br/>12/33/2012: "+isValidDateCheck('12/33/2012');
  document.getElementById("output").innerHTML+="<br/>12/12/2012: "+isValidDateCheck('12/12/2012') ;
  document.getElementById("output").innerHTML+="<br/>02/29/2012: "+isValidDateCheck('02/29/2012') ;
  document.getElementById("output").innerHTML+="<br/>02/29/2013: "+isValidDateCheck('02/29/2013') ;
  document.getElementById("output").innerHTML+="<br/>01/01/2013A: "+isValidDateCheck('01/01/2013A') ;
}