Why is My jQuery '$ is not defined' Even Though It's Included?

JQuery: Addressing the "$ is not defined" Error

Despite referencing jQuery in the site master, you encounter the "$ is not defined" error when using a basic click event. This issue may stem from one of three underlying causes.

Cause 1: Script Loading Issue

Ensure that your JavaScript file is loading correctly into your page. The script reference should resemble this format:

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js" type="text/javascript"></script>

Avoid using attributes like "async" or "defer."

Cause 2: Corrupted jQuery

Check for any alterations or potential overrides to the core jQuery file. Ensure that no plugins have overwritten the "$" variable.

Cause 3: Premature JavaScript Execution

Your JavaScript code may be executing before the page and jQuery are fully loaded. Enclose your jQuery code within the following:

$(document).ready(function () {
  // Your jQuery code here
});

This ensures that your code runs after jQuery initialization.

Additional Considerations

• Plugins that extend the "$" object should be loaded after jQuery core.
• Non-jQuery code can be separated using "document.readyState" instead of placing it within the jQuery ready handler.

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