cannot get textbox value in javascript

Question

I want to retrieve the textbox value in javascript. Simple, but it doesn't work for me, as it returns null/undefined as output. The code:

<asp:TextBox 
    ID = "lbl1" 
    ClientIDMode = "Static" 
    runat = "server"    
    Text = "http://test/test1/dilse.mp4" 
    Visible = "false">
</asp:TextBox>
<asp:Button  
    ID = "btnValidate" 
    runat = "server" 
    Text = "Get Values"   
    OnClientClick = "sourceval(); 
/>

Javascript:

var source = document.getElementById('lbl1').innerHTML;
function sourceval() 
{
    alert(source); 
}

Where are you calling your javascript? It may be that the textbox doesn't exist fully at the time of your calls to access it. — Lee Taylor
– Lee Taylor, Commented Feb 19, 2014 at 20:54

Juan · Accepted Answer · 2014-02-19 20:48:07Z

3

you're not able to get the value of the textbox because you have Visible="false", because of that the textbox doesn't get rendered when the page loads, you could use a HiddenField instead of textbox

<asp:HiddenField ID ="lbl1" ClientIDMode="Static" runat="server" Value="http://test/test1/dilse.mp4" />

answered Feb 19, 2014 at 20:48

Juan

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ps2goat · Accepted Answer · 2014-02-19 21:12:36Z

2

Use the .value property for textboxes. The code for setting OnClientClick is for VB. Use '+' instead of '&' if using C#.

<asp:Button ID="btnValidate" runat="server" Text="Get Values"
         OnClientClick='<%= "sourceval(" & lbl1.ClientID & " );"%>' />

Javascript code:

    function sourceval(controlId) {
          var source = document.getElementById('lbl1').value;
          alert(source); 
    }

edited Feb 19, 2014 at 21:12

answered Feb 19, 2014 at 20:41

ps2goat

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6 Comments

Kamila Over a year ago

HI, thanks for the reply. i used .value but it says undefined in my output.

Sterling Archer Over a year ago

Try passing in source as a parameter?

ps2goat Over a year ago

I just saw the problem -- you're using webforms, which autogenerates random IDs based on html element structure. I will update my code sample

ps2goat Over a year ago

Updated. Let me know if it works--- I can't remember if the page will know that ID at runtime, but I assume it would.

Kamila Over a year ago

hi, its works now as i have changed the textbox to hiddenfield as Juan C Suggested,thanks for your time

|

Neo · Accepted Answer · 2014-02-19 20:42:25Z

0

Just use:

var source = document.getElementById('lbl1').value;

answered Feb 19, 2014 at 20:42

Neo

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