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

When i use DatePicker, jQuery's UI plugin, in an existing .aspx page I get errors that:

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

However, when I copy and paste the same code that creates and uses the datePicker to an HTML file that's also in the same directory as the aspx page, it works flawlessly. This leads me to assume that there are some JS files in the aspx page that's preventing the datePicker or maybe jQuery's UI JS files to load properly.

Can anyone confirm my beliefs or provide any tips on finding the culprit that's interfering with jQuery's UI plugins?



I struggled with a similar problem for hours. It then turned out that jQuery was included twice, once by the program that I was adding a jQuery function to and once by our in-house debugger.


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

var $j = jQuery.noConflict();

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.


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

I have fixed the issue by placing the below three files in the body section of the form at the end.

  <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.6/jquery.min.js" type="text/javascript"></script>
    <script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/jquery-ui.min.js" type="text/javascript"></script>
    <link href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/base/jquery-ui.css" rel="Stylesheet" type="text/css" />

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


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.


I know that this post is quite old, but for reference I fixed this issue by updating the version of datepicker

It is worth trying that too to avoid hours of debugging.



I just had this issue, and moving the JS references and code towards the bottom of the page before the </body> tag fixed it for me.


Also check the permissions for the directory you download the files into. For some reason when I downloaded this, by default it was saved in a folder with no access allowed! It took forever to figure out that was the problem, but I just had to change the permission for the directory and it's contents - setting it so EVERYONE = READ ONLY. Works great now.


I just ran into a similar issue. When I changed my script reference from self-closing tags (ie, <script src=".." />) to empty nodes (ie, <script src=".."></script>) my errors went away and I could suddenly reference the jQuery UI functions.

At the time, I didn't realize this was just a brain-fart of me not closing it properly to begin with. (I'm posting this simply on the chance that anyone else coming across the thread is having a similar issue.)


Some file no load before you call.

For example: Your code:

<%= javascript_include_tag "distpicker.min" %>
<%= javascript_include_tag "distpicker.data.min" %>

Change to this:

<%= javascript_include_tag "distpicker.data.min" %>
<%= javascript_include_tag "distpicker.min" %>

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


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


    @RenderSection("scripts", required: false)

Change footer to

    @RenderSection("scripts", required: false)

I also have struggle for hours looking for solutions on this, and end up on this post. For me it is because sometimes there is no element with id 'datepicker', and because of this error all my javascripts are stoped. it is a little bit tricky, but for the solution i change the code from:

( "#datepickers" ).datepicker();


$( "#datepicker" ).each(function(idx, element){

so even there is no element with id datepicker, the script is not generate an error.


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.


I ran into this problem recently - the issue was that I had included the jQuery UI files in the head tag, but the Telerik library I was using included jQuery at the bottom of the body tag (thus apparently re-initializing jQuery and unloading the UI plugins previously loaded).

The solution was to find out where jQuery was actually being included, and including the jQuery UI scripts after that.


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


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

After (Working):


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