How to pass the selected items from dropdownlist to a Javascript function ?

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Dears ,

I need to pass the selected item from a DropDownList to a Javascript function using OnClientClick to validate it when the botton is cliked on the cilent side.

here is my code that does not work with me , can any body tell me where is the issue:

XML

<asp:Button ID="Save" runat="server" Text="Save" Width="173px"
                        onclick="_Run_Click" OnClientClick="return DateValidation('<%=yFrom.ClientID%>','<%=yTo.ClientID%>')"  />

XML

<script type="text/javascript">
    function DateValidation(yFrom, yTo) {

        var startYear = document.getElementById(yFrom);
        var endYear = document.getElementById(yTo);
        if (startYear != '' && endYear != '')
         {
             if (endYear < startYear)
            {
                alert('Start date cannot be greater than end date');
                 return false;
             }
            else { return true; }
         }
     }
</script>

Thanks,

Posted 26-Apr-12 9:42am

AJ Hoge

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Sandeep Mewara · Answer 1 · 2012-04-26T10:06:00

JavaScript

var startYear = document.getElementById(yFrom);

This gave you just the control object. Sounds like you want to compare the two date value.

Try:

JavaScript

function DateValidation(yFrom, yTo) {

       var startYear = document.getElementById(yFrom);
       var endYear = document.getElementById(yTo);
       if (startYear.value != '' && endYear.value != '')
        {
            if (endYear.value < startYear.value)
           {
               alert('Start date cannot be greater than end date');
                return false;
            }
           else { return true; }
        }
    }

UPDATE:
For date comparison, you need to convert the textbox strings into dates.

Here:

JavaScript

function DateValidation(yFrom, yTo) {

       var startYear = document.getElementById(yFrom);
       var endYear = document.getElementById(yTo);
       if (startYear.value != '' && endYear.value != '')
        {
            Date endDate = new Date(endYear.value);
            Date startDate = new Date(startYear.value);
            if (endDate < startDate)
           {
               alert('Start date cannot be greater than end date');
                return false;
            }
           else { return true; }
        }
    }

Make sure that the textbox has a valid Javascript date or else you will get an error.