Function is undefined using javascript

Question

In my ASP.NET page using the following code:

<asp:ScriptManager  ID="ScriptManager1" runat="server"></asp:ScriptManager>
<script type="text/javascript" language="javascript">
        function ValMail() {
        var txt = document.getElementById("<%= Email.ClientID%>");
        var Resp = <%IsValidEmail(Email.Text)%>;
        if (Resp != false)
            txt.nodeValue = "";
            txt.focus();
            };
    </script>
    <asp:Label ID="EmailLabel" runat="server" AssociatedControlID="Email">E-mail:</asp:Label>
    <asp:TextBox ID="Email" runat="server" TabIndex="4" CssClass="textEntry" CausesValidation="True" ></asp:TextBox>
<asp:Button ID="TestButton" runat="server" OnClientClick="ValMail()" />

My problem is that when I click on the button comes to executes the command OnClientClick="ValMail()"
Holds the execution of the program and throw me an error javascript runtime error: ValMail() is undefined
But even sow I'm clicking Ignore and the code goes into the script executes only the line var Resp = <%IsValidEmail(Email.Text)%>; and nothing from the rest of the code in javascript
I’m completely unfamiliar with javascript coding and most with the thrown errors. Is someone to assist me with that?

You should debug by looking a the source rather than the generating code. What's the output of this code? — plalx
– plalx, Commented Nov 28, 2013 at 21:05
The output is True or False and then I'm trying to handle it inside the script. I set a hold in the code behind and then trying to go step by step and that's why I see that nothing is executed from the other lines of the java code — Lefteris Gkinis
– Lefteris Gkinis, Commented Nov 28, 2013 at 21:11
if IsValidEmail(Email.Text) returns a string, that string needs quoting for javascript variable. As @plalx mentioned...need code browser sees to debug. How it gets generated is irrelevant — charlietfl
– charlietfl, Commented Nov 28, 2013 at 21:12
Where is the function IsValidEmail? Is it on the code behind? — Mateus Schneiders
– Mateus Schneiders, Commented Nov 28, 2013 at 21:13
also...javascript true and false are case sensitive and are lowercase — charlietfl
– charlietfl, Commented Nov 28, 2013 at 21:16

nnnnnn · Accepted Answer · 2013-11-28 21:25:24Z

1

I can't explain the "ValMail() is undefined" error. However, if you use your browser's "View Page Source" option I think you'll find that this line:

var Resp = <%IsValidEmail(Email.Text)%>;

...is sent to the browser as this:

var Resp = True;

or:

var Resp = False;

Either of which is a syntax error in JavaScript because JS is case sensitive and you need a lowercase t or f in the boolean true and false. So either modify that ASP code to put out true or false in all lowercase or add quotes so that JS treats it as a string and then tests as a string with the matching uppercase F:

var Resp = "<%IsValidEmail(Email.Text)%>";
if (Resp != "False")

Which, given that Resp is only used in one place after its declaration, you could shrink down to:

if ("<%IsValidEmail(Email.Text)%>" != "False") {

Also I think you want txt.value, not txt.nodeValue.

Finally, judging by the indenting, I suspect you want both lines under the if to belong to the if, in which case they need to be contained in a block designated by { and } - you currently have no opening { which means only the line immediately after the if belongs to it.

Putting that all together:

function ValMail() {
    var txt = document.getElementById("<%= Email.ClientID%>");
    if ("<%IsValidEmail(Email.Text)%>" != "False") {
        txt.value = "";
        txt.focus();
    }
}

answered Nov 28, 2013 at 21:25

nnnnnn

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5 Comments

Lefteris Gkinis Over a year ago

YES YES YES YES the code now is going perfect and the lines are executed just fine. BUT if I don't want to use the button how can I call the function?

nnnnnn Over a year ago

If you mean that you want the function to be executed automatically when the page loads just call it indirectly with window.onload = ValMail; - or move the <script> element to the end of the page (just before the closing </body> tag) and add ValMail(); immediately after the function to call it - if you call it with ValMail() with the script above the elements it wants to manipulate then it won't work, because if you do it will execute before the browser has parsed those elements.

Lefteris Gkinis Over a year ago

NO no I don't want to executed automatically but I want to executed when I leave the TextBox (with mouse or with TAB). I presume that it must be a way to do that. Because I see now that the Variable Email.Text is not passed to the code behind!!!

Lefteris Gkinis Over a year ago

While I'm debugging it I see that

function ValMail() {         var txt = document.getElementById("LeftNavigationHolder_Email");         if ("" != "False") {             txt.value = "";             txt.focus();         }     }

nnnnnn Over a year ago

Adding onblur="ValMail();" to the text input should run the function when the user tabs or clicks out of the field. Or it might be OnClientBlur=... - it's been years since I did ASP. The code behind only runs when the page is first requested or after a submit.

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