[RESOLVED] Why is this simple code not working?

**HowTo** · Jun 16th, 2010, 08:37 AM

Code:

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>

    <script language="javascript" type="text/javascript">
    function validate()
    {
    if(document.getElementById.('TextBox1').value=="")
    {
    alert("Please enter a value");
    }
    }
    </script>

</head>
<body onload="loading()">
    <form id="form1" runat="server">
        <div>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="validate()" />
        </div>
    </form>
</body>
</html>

no alert box is displayed when i left the textbox blank and clicked the button

please help

**gep13** · Jun 16th, 2010, 08:41 AM

Okay, first up, let's see if your method is getting called at all.

Try this:

Code:

    <script language="javascript" type="text/javascript">
    function validate()
    {
    alert("hi there");
    if(document.getElementById.('TextBox1').value=="")
    {
    alert("Please enter a value");
    }
    }
    </script>

Does that result in an alert appearing?

Are there any JavaScript errors on the page?

Gary

**gep13** · Jun 16th, 2010, 08:42 AM

On another note, have you considered using the built in ASP.Net Validation controls to do this work? Seems to me like this would be a natural fit.

Gary

**HowTo** · Jun 16th, 2010, 08:46 AM

i think the syntax of this code is incorrect :

Code:

if(document.getElementById.('TextBox1').value=="")

please help

**HowTo** · Jun 16th, 2010, 08:47 AM

Code:

<script language="javascript" type="text/javascript">
    function validate()
    {
    alert("hi there");
    if(document.getElementById.('TextBox1').value=="")
    {
    alert("Please enter a value");
    }
    }
    </script>

no.......this code also does not shows any alert box...........

**HowTo** · Jun 16th, 2010, 08:49 AM

Originally Posted by gep13

On another note, have you considered using the built in ASP.Net Validation controls to do this work? Seems to me like this would be a natural fit.

Gary

i agree with you gep

but i am surprised why this bit of code is not working

please help me to get it into work gep

**HowTo** · Jun 16th, 2010, 08:51 AM

but this bit of java script works:

Code:

<&#37;@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>

    <script language="javascript" type="text/javascript">
    function loading()
    {
    alert("hi there");
    
    }
    </script>

</head>
<body onload="loading()">
    <form id="form1" runat="server">
        <div>
            
        </div>
    </form>
</body>
</html>

**HowTo** · Jun 16th, 2010, 08:54 AM

Originally Posted by HowTo

i think the syntax of this code is incorrect :

Code:

if(document.getElementById.('TextBox1').value=="")

please help

i tell this becaues after writing upto this:

Code:

if(document.getElementById.('TextBox1')

when i clicked the "." then the value element is not shown by the intellisense

**danasegarane** · Jun 16th, 2010, 09:02 AM

Code:

if(document.getElementById.('TextBox1').value=="")

This should be

Code:

if(document.getElementById('TextBox1').value=='')

**HowTo** · Jun 16th, 2010, 09:04 AM

Code:

if(document.getElementById('TextBox1').value=="")

works

**gep13** · Jun 16th, 2010, 09:06 AM

Hey,

Okay, having looked at your code a bit closer, and loaded up the JavaScript console in Chrome, I can see two problems with this:

Code:

<head runat="server">
    <title>Untitled Page</title>

    <script language="javascript" type="text/javascript">
    function validate()
    {
    if(document.getElementById.('TextBox1').value=="")
    {
    alert("Please enter a value");
    }
    }
    </script>

</head>
<body onload="loading()">
    <form id="form1" runat="server">
        <div>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="validate()" />
        </div>
    </form>
</body>

Firstly, remove the loading function from the onload event, since it isn't defined, it is causing an error.

Secondly, you have an extra . after getElementById.

It should look like this:

Code:

<head id="Head1" runat="server">
    <title>Untitled Page</title>

    <script language="javascript" type="text/javascript">
    function validate()
    {
    if(document.getElementById('TextBox1').value=="")
    {
    alert("Please enter a value");
    }
    }
    </script>

</head>
<body>
    <form id="form1" runat="server">
        <div>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="validate()" />
        </div>
    </form>
</body>

Hope that helps!!

Gary

**HowTo** · Jun 16th, 2010, 09:07 AM

one more thing:

Code:

<&#37;@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>

    <script language="javascript" type="text/javascript">
    function validate()
    {
    if(document.getElementById('TextBox1').value=="")
    {
    alert("Please enter a value");
    }
    }
    </script>

</head>
<body >
    <form id="form1" runat="server">
        <div>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="validate()" />
        </div>
    </form>
</body>
</html>

if the alertbox is displayed then it means that the textbox is empty and so as soon as the user clicks the ok button of the page,then i done want the page to have a post back...........

in the above code when the user clicks the ok button of the alert box then a postback takes place

how to stop this postback?

**danasegarane** · Jun 16th, 2010, 09:11 AM

Return false if the test fails, else return true to postback

Code:

 <script language="javascript" type="text/javascript">
    function validate()
    {
    if(document.getElementById('TextBox1').value=="")
    {
    alert("Please enter a value");
return false;
    }
return true;
    }
    </script>

</head>
<body >
    <form id="form1" runat="server">
        <div>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="return validate()" />
        </div>
    </form>

**HowTo** · Jun 16th, 2010, 09:18 AM

Code:

<&#37;@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>

    <script language="javascript" type="text/javascript">
    function validate()
    {
    if(document.getElementById('TextBox1').value=="" && document.getElementById('TextBox2').value=="")
    {
    alert("Please enter the UserId and Password");
    return false;
    }
    else if(document.getElementById('TextBox1').value=="")
    {
    alert("Please enter the UserId");
    return false;
    }
    else if(document.getElementById('TextBox2').value=="")
    {
    alert("Please enter the Password");
    return false;
    }
    else
    {
    return true;
    }
    }
    </script>

</head>
<body>
    <form id="form1" runat="server">
        <div>
            <asp:Label ID="Label1" runat="server" Text="UserId :"></asp:Label>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Label ID="Label2" runat="server" Text="Password :"></asp:Label>
            <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button1" runat="server" Text="Submit" OnClientClick="return validate()" />
        </div>
    </form>
</body>
</html>

please have a look at this code........is it ok

**danasegarane** · Jun 16th, 2010, 09:27 AM

Code:

<script language="javascript" type="text/javascript">
    function validate()
    {
    if(document.getElementById('TextBox1').value=="" && document.getElementById('TextBox2').value=="")
    {
    alert("Please enter the UserId and Password");
    return false;
    }
    else if(document.getElementById('TextBox1').value=="")
    {
    alert("Please enter the UserId");
    return false;
    }
    else if(document.getElementById('TextBox2').value=="")
    {
    alert("Please enter the Password");
    return false;
    }
   
    return true;
   
    }
    </script>

**HowTo** · Jun 16th, 2010, 09:30 AM

Code:

<&#37;@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>

    <script language="javascript" type="text/javascript">
    function reset()
    {
    document.getElementById('TextBox1').value=""
    document.getElementById('TextBox2').value=""
    return false;
    }
    </script>

</head>
<body>
    <form id="form1" runat="server">
        <div>
            <asp:Label ID="Label1" runat="server" Text="UserId :"></asp:Label>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Label ID="Label2" runat="server" Text="Password :"></asp:Label>
            <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button2" runat="server" Text="Reset" OnClientClick="return reset()" />
        </div>
    </form>
</body>
</html>

but when i click the button2 in the above code then the two textbox values are set to empty but there is a postback happening........how to stop this?

**danasegarane** · Jun 16th, 2010, 09:39 AM

Set the UsesubmitBehaviour=False for the button..

**HowTo** · Jun 16th, 2010, 10:02 AM

still i cant understand the meaning of this line:

Code:

return false;

whats the difference between

Code:

event.returnValue=false;

and

Code:

return false;

please help

**HowTo** · Jun 16th, 2010, 10:15 AM

ok i had a look at this:
http://www.webdevelopersjournal.com/...jsevents2.html

now i am confused about this bit of code for the reset button:

Code:

function reset()
    {
    document.getElementById('TextBox1').value=""
    document.getElementById('TextBox2').value=""
    return false;
    }

if i dont Set the UsesubmitBehaviour=False for the button ; then why there is a postback after resetting the textbox?

please please help

**gep13** · Jun 16th, 2010, 11:58 AM

Hey,

I have to stress again, why are you going to the extreme of doing this, when all this, and more is done for you in the Validation Controls that ship with ASP.Net?!?

Gary

**HowTo** · Jun 16th, 2010, 12:09 PM

just for learning purpose gep........please help me to clear my concept

**gep13** · Jun 17th, 2010, 01:11 AM

Bottom line is, if you are using the OnClientClick property of the button, and you are trying to prevent a PostBack from happening, then you need to have your JavaScript function return false. If it doesn't, then the PostBack will occur.

Part of the issue here, I suspect, is the fact that you have JavaScript errors in your function. Namely, the lines are not terminating with a ;.

What browser are you using for debugging your application? These JavaScript errors should be getting shown to you.

Gary

**HowTo** · Jun 17th, 2010, 08:27 AM

ok you suggested me to terminate the lines with a ; and i did this:

Code:

function reset()
    {
    document.getElementById('TextBox1').value="";
    document.getElementById('TextBox2').value="";
    return false;
    }

  <asp:Button ID="Button2" runat="server" Text="Reset" OnClientClick="return reset()" />

still the button2 click causes the postback

**HowTo** · Jun 17th, 2010, 08:31 AM

Originally Posted by gep13

What browser are you using for debugging your application?
Gary

IE7

Originally Posted by gep13

These JavaScript errors should be getting shown to you.
Gary

how to see the errors?

**gep13** · Jun 17th, 2010, 09:53 AM

Originally Posted by HowTo

how to see the errors?

http://www.testingreflections.com/node/view/4009

**gep13** · Jun 17th, 2010, 09:56 AM

Originally Posted by HowTo

still the button2 click causes the postback

This:

Code:

<head runat="server">
    <title></title>
    <script language="javascript" type="text/javascript">
        function HowToreset() {
            return false;
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Button ID="Button1" runat="server" Text="Reset" OnClientClick="return HowToreset()" />
        <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    </div>
    </form>
</body>

Does not cause a PostBack.

i.e. watch the names that you are using for your functions.

Gary

**gep13** · Jun 17th, 2010, 10:06 AM

Also, you might want to think about using a standing html input element, rather than a server button, if you are not actually doing anything on the server side.

Gary

**HowTo** · Jun 17th, 2010, 11:24 PM

Originally Posted by gep13

watch the names that you are using for your functions.

Gary

i cant follow what you tried to mean with the function names

**danasegarane** · Jun 17th, 2010, 11:48 PM

If you are are you simply want to Reset the values then Consider using the HTML Reset button

Code:

<input id="Reset1" type="reset"
                value="reset" />

**danasegarane** · Jun 18th, 2010, 12:01 AM

Just Found the Problem. The Function name was causing the Problem..

Change the function name...
It works

Code:

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>Untitled Page</title>

      <script language="javascript" type="text/javascript">
    function resets()
    {
    document.getElementById('TextBox1').value="";
    document.getElementById('TextBox2').value="";
    return true;
    }
    </script>

</head>
<body>
    <form id="form1" runat="server">
        <div>
            <asp:Label ID="Label1" runat="server" Text="UserId :"></asp:Label>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Label ID="Label2" runat="server" Text="Password :"></asp:Label>
            <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button2" runat="server" Text="Reset" OnClientClick="return resets();" />
        </div>
    </form>
  
</body>
</html>

**gep13** · Jun 18th, 2010, 01:12 AM

Originally Posted by danasegarane

Just Found the Problem. The Function name was causing the Problem..

Change the function name...
It works

That's what I said

Gary

**gep13** · Jun 18th, 2010, 01:14 AM

Originally Posted by HowTo

i cant follow what you tried to mean with the function names

You have a JavaScript function named "reset". This must be some form of reserved word in JavaScript, as when you use it, it does not function the way it should. This was shown in your other thread where you were using a function named "open".

In my case, I renamed your function to "HowToreset", and Dana renamed it to be "resets", in both cases, this made the function start working as expected.

Gary

**danasegarane** · Jun 18th, 2010, 02:09 AM

Originally Posted by gep13

That's what I said

Gary

Let's wait for the reply

**HowTo** · Jun 18th, 2010, 11:20 AM

Now it works

**HowTo** · Jun 18th, 2010, 11:21 AM

i need a suggestion:I am working hard to learn javascript since after this i want to go for the ajax........so is it a good idea to learn javascript before going for the ajax?

**gep13** · Jun 18th, 2010, 11:59 AM

Yes, I would say that it is essential, yes.

You will like need to become familiar in both JavaScript and jQuery.

Gary

**HowTo** · Jun 18th, 2010, 12:26 PM

what is jQuery all about?how to use it in asp.net?

**gep13** · Jun 18th, 2010, 01:03 PM

First two hits in google:

http://weblogs.asp.net/scottgu/archi...microsoft.aspx

http://dotnetslackers.com/articles/a...h-asp-net.aspx

Gary

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