Javascript's equilvalent of DateDiff Function?

[fjober]

try this function please, return true if the difference is less than a year:

<script type="text/javascript">
    // mm/dd/yyyy
    var validDate = /^\d{1,2}\/\d{1,2}\/\d{4}$/;
    function dateDifference(date1, date2)
    {
        if (validDate.test(date1) && validDate.test(date1)) {
            date1Numbers = date1.split("/");
            date2Numbers = date2.split("/");
            var month1 = date1Numbers[0];
            var month2 = date2Numbers[0];
            var day1 = date1Numbers[1];
            var day2 = date2Numbers[1];
            var yearDif = Math.abs(date1Numbers[2] - date2Numbers[2]);
            if (yearDif <= 1) {
                if (yearDif == 1) {
                    if (month2 <= month1) {
                        if (month2 == month1) {
                            if (day2 <= day1) {
                                calculateDiff(date1Numbers, date2Numbers);
                                return true;
                            } else {
                                return false;
                            }
                        } else {
                            calculateDiff(date1Numbers, date2Numbers);
                        }
                    } else {
                        return false;
                    }   
                } else {
                    calculateDiff(date1Numbers, date2Numbers);
                }
            } else {
                return false;
            }
        } else {
            return false;
        }  
    }
    
    function calculateDiff(date1Numbers, date2Numbers)
    {
        var resultAsDays = 0;
        var day1 = parseInt(date1Numbers[1]);
        var month1 = parseInt(date1Numbers[0]);
        var year1 = parseInt(date1Numbers[2]);
        var day2 = parseInt(date2Numbers[1]);
        var month2 = parseInt(date2Numbers[0]);
        var year2 = parseInt(date2Numbers[2]);
        
        if (year1 == year2) {
            resultAsDays += (Math.abs(month2 - month1)) * 30;
            resultAsDays -= day1;
        } else {
            if (month1 == month2) {
                resultAsDays += 330;
            } else {
                resultAsDays += (12 - (month1 - 1) + month2) * 30;
                resultAsDays -= day1;
            }
        }
        resultAsDays += day2;
        window.alert(resultAsDays);
    }
    </script>

<input type="text" id="date1" />
<input type="text" id="date2" />

<input type="button" value="is valid" onclick="window.alert(dateDifference(document.getElementById('date1').value, document.getElementById('date2').value));" />

hope this to be useful

please try it, I have tested it on some dates and I think it works good

regards

Feras Jobeir