Why Is My jQuery '$' Undefined, and How Can I Fix It?

Uncaught ReferenceError: jQuery "$" is Not Defined

When attempting to use jQuery in a script, you may encounter the error "Uncaught ReferenceError: $ is not defined." This issue typically occurs when the sequence of jQuery script references is incorrect.

To resolve this problem:

1. Ensure that the reference to the core jQuery library, "jquery.js," is placed before any other jQuery-related scripts.
2. Check that the referenced version of jQuery is compatible with the version of jQuery UI being used. If using jQuery UI 1.5.2, for example, ensure you have included jQuery 1.2.6 or later.
3. Avoid conflicts by ensuring that no other JavaScript libraries or scripts are overriding the "$" variable.

By following these steps, you can ensure that jQuery is properly defined and available for use in your scripts.

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