TypeError: $(...).datepicker is not a function in jQuery

# TypeError: $(...).datepicker is not a function in jQuery

The "$(...).datepicker is not a function" jQuery error occurs for multiple reasons:

Forgetting to include the jQuery UI library.
Loading the jQuery UI library before the jQuery library.
Loading the jQuery library twice.
Specifying an incorrect path to the jQuery files.
Using a custom jQuery UI library that doesn't have a date picker.

To solve the error, make sure to load the jQuery library before loading the jQuery UI library.

The libraries have to be loaded only once on the page, otherwise, the error is thrown.

index.html

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <!-- ✅ Load CSS file for jQuery UI  -->
    <link
      href="https://code.jquery.com/ui/1.12.1/themes/ui-lightness/jquery-ui.css"
      rel="stylesheet"
    />

    <!-- ✅ load jQuery ✅ -->
    <script
      src="https://code.jquery.com/jquery-3.6.0.min.js"
      integrity="sha256-/xUj+3OJU5yExlq6GSYGSHk7tPXikynS7ogEvDej/m4="
      crossorigin="anonymous"
    ></script>

    <!-- ✅ load jquery UI ✅ -->
    <script
      src="https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js"
      integrity="sha512-uto9mlQzrs59VwILcLiRYeLKPPbS/bT71da/OEBYEwcdNUk8jYIy+D176RYoop1Da+f9mvkYrmj5MCLZWEtQuA=="
      crossorigin="anonymous"
      referrerpolicy="no-referrer"
    ></script>
  </head>

  <body>
    <p>Date: <input type="text" id="datepicker" /></p>

    <script src="index.js"></script>
  </body>
</html>

Notice that we first loaded the jQuery library and then the jQuery UI library.

The order is very important because if you load the UI library before jQuery, you would get the error.

Here's the related JavaScript code.

index.js

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$(function () {
  $('#datepicker').datepicker();
  $('#datepicker').datepicker('show');
});

If you load the page, you will see the date picker open.

The order in which the scripts are loaded is very important:

Load the jQuery library first.
Load the jQuery UI library second.
Load your personal JS script (e.g. index.js).

Make sure you don't include the jQuery script twice on the same page. This would re-run the initialization process and would cause the error.

If you use a custom jQuery UI library, make sure it includes a date picker.

Lastly, if you are loading the jQuery libraries from files on your local filesystem, make sure the specified paths to the files are correct.

You can check if you're loading the scripts correctly by opening your Developer tools by pressing F12 and clicking on the Console tab.

If you see any 404 errors related to loading the jQuery scripts, then the path to the file is incorrect.

# Conclusion

To solve the "$(...).datepicker is not a function" jQuery error, make sure to load the jQuery library before loading the jQuery UI library.

The libraries have to be loaded only once on the page, otherwise, the error is thrown.

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TypeError: $(...).datepicker is not a function in jQuery

# TypeError: $(...).datepicker is not a function in jQuery

# Conclusion

Borislav Hadzhiev