jQuery UI " $("#datepicker").datepicker is not a function"

If there is another library that is using the $ variable, you can do this:

var $j = jQuery.noConflict();
$j("#datepicker").datepicker();

Also make sure your javascript includes are in the correct order so the jquery core library is defined before the jquery.ui. I've had that cause issues.

This error usually appears when you're missing a file from the jQuery UI set.

Double-check that you have all the files, the jQuery UI files as well as the CSS and images, and that they're in the correctly linked file/directory location on your server.

If you think that there is a conflict you can use jQuery.noConflict() in your code. Details are in the docs.

REFERENCING MAGIC - SHORTCUTS FOR JQUERY

If you don't like typing the full "jQuery" all the time, there are some alternative shortcuts:

Reassign jQuery to another shortcut var $j = jQuery; (This might be the best approach if you wish to use different libraries) Use the following technique, which allows you to use $ inside of a block of code without permanently overwriting $:

(function($) { /* some code that uses $ */ })(jQuery)

Note: If you use this technique, you will not be able to use Prototype methods inside this capsuled function that expect $ to be Prototype's $, so you're making a choice to use only jQuery in that block. Use the argument to the DOM ready event:

jQuery(function($) { /*some code that uses $ */ });

Note: Again, inside that block you can't use Prototype methods

Thats from the end of the docs and might be useful to you

Go for the obvious first: Are you referencing well the jquery-ui.js file?

Try using the network tab of firebug to find if it is loaded, or the Information\View javascript code of the Web Developer Toolbar.

Have you tried using Firebug to 1) determine that there are no Javascript errors and 2) that the #datepicker element exists on the page?

Most likely there is an error prior to the datepicker call that is preventing the datepicker call from executing.

For me it was just necessary to remove the "defer" property from the declaration of my script

I could fix this problem removing the jquery bundle on the _Layout.cshtml

Header

    <script src="~/Scripts/jquery-1.10.2.js"></script>
    <script src="~/Scripts/kendo/2015.2.902/kendo.all.min.js"></script>
    ...

Footer

    @Scripts.Render("~/bundles/jquery")
    @Scripts.Render("~/bundles/bootstrap")
    @RenderSection("scripts", required: false)

Change footer to

    @Scripts.Render("~/bundles/bootstrap")
    @RenderSection("scripts", required: false)

Have you tried using $("#<%= txtDateElementId.ClientID %>").datepicker(); instead of $("#txtDateElementId").datepicker(); when selecting an element by ID using JQuery.

Old question - newer version of .NET (4.5.6) - same issue - new answer

Using NuGet

Make sure you have the following installed via NuGet:

• jQuery
• AspNet.ScriptManager.jQuery
• jQuery.UI.Combined
• AspNet.ScriptManager.jQuery.UI.Combined

Install them from here [ Tools > NuGet Package Manager > Manage NuGet Packages for Solution ]

Then, jquery and jquery.ui.combined should be added to your ScriptManager in Site.Master. Will look something like this:

    <asp:ScriptManager runat="server">
        <Scripts>
            <%--To learn more about bundling scripts in ScriptManager see https://go.microsoft.com/fwlink/?LinkID=301884 --%>
            <%--Framework Scripts--%>
            <asp:ScriptReference Name="MsAjaxBundle" />
            <asp:ScriptReference Name="jquery" />
            <asp:ScriptReference Name="jquery.ui.combined" />
            <asp:ScriptReference Name="bootstrap" />
            <asp:ScriptReference Name="WebForms.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebForms.js" />
            <asp:ScriptReference Name="WebUIValidation.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebUIValidation.js" />
            <asp:ScriptReference Name="MenuStandards.js" Assembly="System.Web" Path="~/Scripts/WebForms/MenuStandards.js" />
            <asp:ScriptReference Name="GridView.js" Assembly="System.Web" Path="~/Scripts/WebForms/GridView.js" />
            <asp:ScriptReference Name="DetailsView.js" Assembly="System.Web" Path="~/Scripts/WebForms/DetailsView.js" />
            <asp:ScriptReference Name="TreeView.js" Assembly="System.Web" Path="~/Scripts/WebForms/TreeView.js" />
            <asp:ScriptReference Name="WebParts.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebParts.js" />
            <asp:ScriptReference Name="Focus.js" Assembly="System.Web" Path="~/Scripts/WebForms/Focus.js" />
            <asp:ScriptReference Name="WebFormsBundle" />
            <%--Site Scripts--%>
        </Scripts>
    </asp:ScriptManager>

This solved my same issue. Thank you.

(”#datepicker“).datepicker is not a function

I also ran into this problem a few days ago. It occurs probably because of having the jquery link more than once in the file. Try searching the whole file for that duplicate content.

It will look somewhat like this:

<script src="https://code.jquery.com/jquery-1.12.1.js"></script>

Keep one in the <head></head> tag and remove all the rest. This will fix the issue.

For those using Laravel, the default app.js has a defer in its declaration.
DELETE IT

referencing jQuery twice might cuase the issue.

Your code needs to include JQuery UI, paste this after your jQuery script:

<link rel="stylesheet" href="https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/themes/smoothness/jquery-ui.css">
<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js"></script>

If you want higher security then you can download version 1.13 on your PC, as 1.12 has some vulnerabities and Google doesn't host the newest version yet.

For me the error was happening because of invalid date format:

Invalid code:

<script>
    $('#targetDate').datepicker({
        format : 'dd/MM/yyyy'
    });
</script>

Valid code:

<script>
    $('#targetDate').datepicker({
        format : 'dd/mm/yyyy'
    });
</script>

Notice the MM. Please see if the format of your date is correct. Hope it helps!

In my case, it was solved by changing the import order of the following scripts: Before (Not work):

After (Working):