Calling Javascript on a Dropdown list

  • Thread starter Thread starter Guest
  • Start date Start date
G

Guest

I have a dropdown list as below.

I add an onchnage attribute in my codebehind to call some Javascript.

I want to get the selected text from my dropdown. What am I doing wrong below?

<asp:DropDownList ID="ddlStatus" runat="server" />

In my codebehind

ddlStatus.Attributes["onchange"] = "javascript:SetDateFields();";



<script language="javascript" type="text/javascript">

function SetDateFields()

{

var statusList = document.getElementById("ddlStatus");


var selectedStatus = statusList.options[statusList.selectedIndex].value;


}

</script>
 
C said:
I have a dropdown list as below.

I add an onchnage attribute in my codebehind to call some Javascript.

I want to get the selected text from my dropdown. What am I doing wrong below?
Click to expand...

Why do you think that you are doing something wrong? What happens when
you try to use the code? Do you get any error message? Have you enabled
Javascript error messages in the browser?
<asp:DropDownList ID="ddlStatus" runat="server" />

In my codebehind

ddlStatus.Attributes["onchange"] = "javascript:SetDateFields();";
Click to expand...

The "javascript:" protocol is only used when you put Javascript in an
URL. The only reason that you don't get an error message when you use it
elsewhere, is that it becomes a label instead.

ddlStatus.Attributes["onchange"] = "SetDateFields();";
<script language="javascript" type="text/javascript">

function SetDateFields()

{

var statusList = document.getElementById("ddlStatus");
Click to expand...

Have you checked that this is the actual id that the element gets in the
html code?
var selectedStatus = statusList.options[statusList.selectedIndex].value;
Click to expand...

You are getting the value instead of the text.
 
Hi,

C wrote:

<script language="javascript" type="text/javascript">
Click to expand...

Additionally to Göran's remarks, the "language" attribute is deprecated.
You can safely remove it and use only the "type" attribute.

Greetings,
Laurent
 
As mentioned on the other forum, aside from the issues adressed by the
others, you are doing anything wrong. Try putting alert(selectedStatus) just
before the closing brace and you will see the value.
Peter
 
Hi there,

In addition to Goran's reply, please find working snippet below:

-- begin aspx code --

<asp:DropDownList ID="ddlStatus" runat="server"
AutoPostBack="false" OnChange="SetDateFields()">
<asp:ListItem Text="Status1" Value="Value1"/>
<asp:ListItem Text="Status2" Value="Value2"/>
<asp:ListItem Text="Status3" Value="Value3"/>
</asp:DropDownList>

<script type="text/javascript">
function SetDateFields()
{
var statusList = document.getElementById('<%=ddlStatus.ClientID %>');
var selectedStatus = statusList.options[statusList.selectedIndex].text;

alert('selected status is : ' + selectedStatus);
}
</script>
-- end aspx code --

Note you have to use control.ClientID to get the valid ID (ClientID contains
all the parent controls ids - if i didnt use it and moved dropdown list to a
Panel control it'd stop work). You may be wondering why i put OnChange
attribute to drop down list declaration. This is allowed (even if you get a
warning from schema validation) and it's called 'expando'.

Hope it's clear now


Milosz
 
Hi there,

In addition to Goran's reply, please find working snippet below:

-- begin aspx code --

<asp:DropDownList ID="ddlStatus" runat="server"
AutoPostBack="false" OnChange="SetDateFields()">
<asp:ListItem Text="Status1" Value="Value1"/>
<asp:ListItem Text="Status2" Value="Value2"/>
<asp:ListItem Text="Status3" Value="Value3"/>
</asp:DropDownList>

<script type="text/javascript">
function SetDateFields()
{
var statusList = document.getElementById('<%=ddlStatus.ClientID %>');
var selectedStatus = statusList.options[statusList.selectedIndex].text;

alert('selected status is : ' + selectedStatus);
}
</script>
-- end aspx code --

Note you have to use control.ClientID to get the valid ID (ClientID contains
all the parent controls ids - if i didnt use it and moved dropdown list to a
Panel control it'd stop work). You may be wondering why i put OnChange
attribute to drop down list declaration. This is allowed (even if you get a
warning from schema validation) and it's called 'expando'.

Hope it's clear now


Milosz
 
Hi,

U can acheive that by writing

ddlStatus.Attributes.Add("onchange","javascript:SetDateFields()")


Bhaskar
 
Hi,

Bhaskardeep said:
Hi,

U can acheive that by writing

ddlStatus.Attributes.Add("onchange","javascript:SetDateFields()")
Click to expand...

This is the same as what the OP did

ddlStatus.Attributes["onchange"] = "javascript:SetDateFields();";

Additionally, had you read previous answers, you would have seen that
you should never use "javascript:", except in very very specific cases.

HTH,
Laurent
 
Back
Top