$Find returns null

Question

I have the following JScript on a page

<script type="text/javascript">
    function ProcessButtonDisable() {
        var button = $find("<%=ProcessButton.ClientID %>");
        button.disabled = true;
            }
</script>

and later

<asp:Button ID="ProcessButton" Text="Process All" runat="server" OnClick="Process_Click" OnClientClick="ProcessButtonDisable()" />

when running the page and firing off the button i get

Microsoft JScript runtime error: Unable to set value of the property 'disabled': object is null or undefined

and the dynamic page has converted it to:

<script type="text/javascript">
    function ProcessButtonDisable() {
        var button = $find("ctl00_ctl00_BodyContentPlaceHolder_MainContentPlaceHolder_ProcessButton");
        button.disabled = true;
    }
</script>

<input type="submit" name="ctl00$ctl00$BodyContentPlaceHolder$MainContentPlaceHolder$ProcessButton" value="Process All" onclick="ProcessButtonDisable();" id="ctl00_ctl00_BodyContentPlaceHolder_MainContentPlaceHolder_ProcessButton" />

as the control is clearly defined and the client id seems to be returning the correct id i don't know whats wrong

Any help?

ps in case this is not clear from the code the purpose of this is to prevent he user from clicking on the and resending the request before the page has time to reload after the initial click

Implacental

try $.find() (mind the dot) or $(document).find() – Millner

now button has the value of [], and while it doesn't error it doesn't disable the button either – Implacental

also, find returns an array....$.find()[0] would give you the button – Millner

my answer should help you anyways :) – Millner

$.find is empty array $(document).find() has data – Implacental

Answer 1

You need to use the dot notation, as find() is a jQuery function, like this:

<script type="text/javascript">
    function ProcessButtonDisable() {
        var button = $.find("<%=ProcessButton.ClientID %>");
        button.disabled = true;
    }
</script>

Also, if you are going to take the trouble to look up the DOM element in your jQuery logic, then do not bother wiring up the OnClientClick on the server control; either wire up the click event via jQuery or pass the element itself to the JavaScript function:

Using jQuery to wire up the click event (recommended):

<script type="text/javascript">
    $(document).ready(function() {
         $("#<%=ProcessButton.ClientID%>").click(function() {
            $(this).disabled = true;
         });
    });
</script>

Using the OnClientClick attribute to wire up the click event and pass the element (not recommended):

<asp:Button ID="ProcessButton" Text="Process All" runat="server" OnClick="Process_Click" 
    OnClientClick="ProcessButtonDisable(this)" />

<script type="text/javascript">
    function ProcessButtonDisable(elem) {
        elem.disabled = true;
    }
</script>

Contention

It is not recommended, because it unnecessarily couples the JavaScript to the DOM element in the markup itself. This clutters the markup, especially if you have multiple buttons that are handled by the same event handler code. Whereas with unobtrusive JavaScript, you could make a selector that applies the same click handler to several different buttons that share the same characteristic (i.e. being a button, or having the same class attribute). This makes the JavaScript logic separate from the actual markup and you do not need to have the same function call in multiple button tags. – Contention

It is just not recommended, but don't take that to mean you cannot do it, because it will work. There is a big push to keep JavaScript and HTML elements defined away from each other, but it comes with the inconvenience of having to look at two files or sections of files independently when debugging your code or worse debugging someone else's code. I probably should not have put the recommendede and not recommended comments in my answer. My apologies, but glad it worked for you. :-) – Contention

No worries its like the old saw about the difference between a novice and an expert, a novice doesn't know the rules and an expert knows when to ignore them. i'm a novice web developer so i need to learn the rules and the reasons for them – Implacental

Answer 2

-1 to all the previous answers for assuming JQuery. $find is a function defined by the Microsoft AJAX Library. It "provides a shortcut to the findComponent method of the Sys.Application class" which gets "a reference to a Component object that has been registered with the application through the addComponent method". Try using $get() instead, which "Provides a shortcut to the getElementById method of the Sys.UI.DomElement class."

This page explores both functions in detail: The Ever-Useful $get and $find ASP.NET AJAX Shortcut Functions

Itis

it seems rather petty to downvote everyone elses answers because they glossed over a point of complexity. a down votes is for when the answer provided is completely useless and wrong, so as your answer is mostly complaining about incorrect terminology with almost no effort to answer the original question yours is as deserving of a down vote as all the answers your down voted, so i can understand if they are retaliatory – Implacental

@Implacental It's not petty at all. It is the purpose of the down voting function. They are answering an assumed question, not the question that was asked. Terminology has nothing to do with it. $Find is from a completely unrelated javascript library; the MS AJAX JS library, not JQuery. My answer has 1 short sentence describing my down vote and why the other answers are wrong (which comes out to 10% of my answer, not "most"). Evidently that was too little, if anything, because you obviously haven't taken time to understand the question or the answers. – Itis

Here is the correct link: gsravisankar.blogspot.co.za/2010/12/… – Guthry

@Itis I had to downvote yours because it doesn't necessarily answer the original question and assumes $get is a substitute for $find which it's not – Disaccord

@Disaccord Hmm, it's been 9 years, but it still seems to answer the question to me. OP was getting null when trying to get the button. I suggested $find was not the appropriate method to call and $get should get the reference to the button. That's not to suggest they are interchangeable, rather, the opposite. How would you suggest this answer can be improved? – Itis

Answer 3

$find is differ from $.find. The first one is provides a shortcut to the findComponent method of the Sys.Application class which defined by the Microsoft AJAX Library. while the second is API method from jQuery which get the descendants of each element in the current set of matched elements, filtered by a selector, jQuery object, or element.

So, $find has to find Component not html DOM. and ajax Library has to be defined.

For more information:

http://msdn.microsoft.com/en-us/library/vstudio/bb397441(v=vs.100).aspx

http://api.jquery.com/find/

Teahan

Clarity is important in programming, do you mean to be writing $Find or $find? – Nasal

Answer 4

try this:

<script type="text/javascript">
    function ProcessButtonDisable() {
        var button = $("#<%=ProcessButton.ClientID %>");
        button.disabled = true;
    }
</script>

[edit] or

<script type="text/javascript">
    function ProcessButtonDisable() {
        $("#<%=ProcessButton.ClientID %>").attr("disabled", "disabled");
    }
</script>

Millner

returns Microsoft JScript runtime error: Unable to get value of the property 'attr': object is null or undefined – Implacental

Answer 5

You have to select what you are "finding" in first. For example, if you select document then use the method "find" you should have the result you want.

<script type="text/javascript">
    function ProcessButtonDisable() {
        var button = $(document).find(("<%=ProcessButton.ClientID %>");
        button.disabled = true;
        }
</script>

Shepperd

Answer 6

disabled is not a jQuery object property it is a DOM element property. Try using either:

$('selector').get(0).disabled = true

, or

$('selector').attr('disabled','disabled');

Beer

Not overly relevant as if the object is null you can't change attr either – Implacental

NREs come from attempting to access properties from invalid implicit parameters (null in this case). But as you have found out from @[Karl Anderson]'s answer you were attempting to access a DOM property from a Microsoft AJAX library component object resulting from the $find shortcut call. Karl's first two answers still didn't work for you because he too was trying to access a DOM property from a non-DOM (jQuery) object. – Beer