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Join Date: Aug 2007
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Junior Poster in Training
getElementById not retreiving values from ASP textbox I have been trying to use
to get the value of this text box
but get an object required error in IE and document.getElementById("tbDescription") has no properties in FireFox. I have tried using the single, double quotes, and nothing around the tbDescription in the javascript function, but none of the 3 helps.
javascript Syntax (Toggle Plain Text)
asp Syntax (Toggle Plain Text)
but get an object required error in IE and document.getElementById("tbDescription") has no properties in FireFox. I have tried using the single, double quotes, and nothing around the tbDescription in the javascript function, but none of the 3 helps.
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Join Date: Aug 2007
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Re: getElementById not retreiving values from ASP textbox I figured it out...
When I looked at the source code on the actual webpage the text box id changed from id=tbdescription to
ctl00_ContentPlaceHolderMain_tbDescription. So once I changed the code from this:
to this everything worked fine. The actual text box in the code is still .
When I looked at the source code on the actual webpage the text box id changed from id=tbdescription to
ctl00_ContentPlaceHolderMain_tbDescription. So once I changed the code from this:
<script language="javascript" type="text/javascript">
function check()
{
var maxLen = 50;
if (document.getElementById('tbDescription').value.length >= maxLen)
{
var msg = "You have reached your maximum limit of characters allowed";
alert(msg);
document.getElementById('tbDescription').value = document.getElementById('tbDescription').value.substring(0, maxLen);
}
}
</script>
<script language="javascript" type="text/javascript">
function check()
{
var maxLen = 50;
if (document.getElementById('ctl00_ContentPlaceHolderMain_tbDescription').value.length >= maxLen)
{
var msg = "You have reached your maximum limit of characters allowed";
alert(msg);
document.getElementById('ctl00_ContentPlaceHolderMain_tbDescription').value = document.getElementById('ctl00_ContentPlaceHolderMain_tbDescription').value.substring(0, maxLen);
}
}
</script>
<asp:TextBox id="tbDescription" runat="server" Height="78px" TextMode="MultiLine" onkeypress="check()" Width="363px"></asp:TextBox>
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Join Date: Feb 2005
Location: Braintree, UK
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A better solution is this:
and for the TextBox have:
Now it doesn't matter what the textbox is called as it passes a reference to itself to the javascript function. This is loosley coupled programming the function's responsibilty is to check the length of a textbox value and that's it, it shouldn't have 'knowledge' of the textbox's id.
javascript Syntax (Toggle Plain Text)
and for the TextBox have:
<asp:TextBox id="tbDescription" runat="server" Height="78px" TextMode="MultiLine" onkeypress="check(this)" Width="363px"></asp:TextBox>Now it doesn't matter what the textbox is called as it passes a reference to itself to the javascript function. This is loosley coupled programming the function's responsibilty is to check the length of a textbox value and that's it, it shouldn't have 'knowledge' of the textbox's id.
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What if I wanted to use information from another textbox? Is there a way to call that text box with just the id or do I always have to check the source code and repaste that in my code?
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Join Date: Feb 2005
Location: Braintree, UK
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oops there's an error in my source
That's exactly what my solution does. You can use
<asp:TextBox id="tbDescription" runat="server" Height="78px" TextMode="MultiLine" onkeypress="check_length(this);" Width="363px"></asp:TextBox>
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What if I wanted to use information from another textbox?
That's exactly what my solution does. You can use
onkeypress="check_length(this);" for any textbox, no matter what its id is. Last edited by hollystyles : Sep 18th, 2007 at 3:23 am.
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Join Date: Aug 2007
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Your solution works for the textbox that the function call is initiated in only, right? If I wanted to use that value and another value from another text box or more in one function I could pass the value of one of the functions with "this", but how would I get the other textbox values?
Something like this:
Your solution worked great for what I originally needed, but I was wondering what I could do to use other textboxes too without having to check the source code to see what got added to the textbox2 id.
Something like this:
<asp:TextBox id="tbDescription" runat="server" Height="78px" TextMode="MultiLine" onkeypress="check_length(this);" Width="363px"></asp:TextBox>
function check(textbox)
{
var x = textbox.value;
alert(x);
var y = document.getElementById("textbox2").value;
alert(y);
}Your solution worked great for what I originally needed, but I was wondering what I could do to use other textboxes too without having to check the source code to see what got added to the textbox2 id.
Last edited by rrocket : Sep 18th, 2007 at 8:11 am.
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Join Date: Feb 2005
Location: Braintree, UK
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You can get the
Change the javascript function to have an extra parameter:
EDIT: missing bracket in serverside code snippet.
this.tbDescription.UniqueID server side. UniqueID is the hierarchical id the control will have when rendered to the client. You could add the onkeydown attribute serverside something like:public void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
this.tbDescription.Attributes.Add("onkeydown", "check_length(this, document.getElementById('" + this.tbOtherTextBox.UniqueID + "'));");
}
}Change the javascript function to have an extra parameter:
function check(textbox1, textbox2)
{
var x = textbox1.value;
var y = textbox2.value;
alert(x + y);
}EDIT: missing bracket in serverside code snippet.
Last edited by hollystyles : Sep 18th, 2007 at 8:30 am.
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