Subtract dates in Javascript

Question

My code is supposed to subtract dates (enddate-startdate) but nothing's happening and can't figure out where the problem is.

 <script type="text/javascript">
        function subtractDate()
        {

            var sDate = Date.parse("<%=txtStartDate.Text%>");
            var eDate = Date.parse("<%=txtEndDate.Text%>");
            var resultDate = document.getElementById("<%=txtnumberOfDaysCovered.ClientID%>")
            if (document.getElementById(sDate) < document.getElementById(eDate)) {
                var timeDiff = eDate.Subtract(sDate);
                resultDate = Math.floor(timeDiff / (1000 * 60 * 60 * 24));


            }
        }
    </script>

I already tried to call it behind

    protected void txtStartDate_TextChanged(object sender, EventArgs e)
    {

       // SubtractDateStartDateChange();
        Page.ClientScript.RegisterStartupScript(this.GetType(), "CallMyFunction", "subtractDate(this.Id)", true);
    }

    protected void txtEndDate_TextChanged(object sender, EventArgs e)
    {
        //SubtractDate();
        Page.ClientScript.RegisterStartupScript(this.GetType(), "CallMyFunction", "subtractDate(this.Id)", true);
    }

You don't do anything with the result that `subtractDate` calculates. Therefore nothing happens. — Richard, May 15 '18 at 07:47
Nothing will happen as you are just calculation resultDate and not using it anywhere — PSK, May 15 '18 at 07:47
What is the value returned by `"<%=txtStartDate.Text%>"`? Hopefully you're aware of the pitfalls of using the built-in parser, see [*Why does Date.parse give incorrect results?*](https://stackoverflow.com/questions/2587345/why-does-date-parse-give-incorrect-results) — RobG, May 15 '18 at 08:25
i'm using a date picker for my date values. @psk resultDate is just a textbox that suppose to have the timediff value converted into days(integer) — XPRGMRX, May 16 '18 at 03:13

score 2 · Answer 1 · answered May 15 '18 at 13:47

Your passing subtractDate(this.Id) from the code behind part, But the function subtractDate() not expecting any parameter on the client side. I think, due to this the function is not working.function subtractDate() expecting an Id parameter, Change the function with a param.

Hope function as follows will work.

function subtractDate(var id)
        {

            var sDate = Date.parse("<%=txtStartDate.Text%>");
            var eDate = Date.parse("<%=txtEndDate.Text%>");
            var resultDate = document.getElementById("<%=txtnumberOfDaysCovered.ClientID%>")
            if (document.getElementById(sDate) < document.getElementById(eDate)) {
                var timeDiff = eDate.Subtract(sDate);
                resultDate = Math.floor(timeDiff / (1000 * 60 * 60 * 24));


            }
        }

Subtract dates in Javascript

1 Answers1