Why Am I Getting a '$ is not defined' Error in jQuery?

jQuery Error: "$ is not defined"

When encountering the "$ is not defined" error in jQuery, indicating that jQuery is not accessible, there are three potential causes:

1. Improper JavaScript File Loading

Ensure that your jQuery script is properly loaded into the page. It should appear as follows:

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

Additionally, it should not have async or defer attributes.

2. Corrupted jQuery Version

Check if your jQuery file is intact. A corrupted version can result from manual edits to the core file or plugin interference.

3. Premature Script Execution

Ensure that your JavaScript code is executed after jQuery is fully loaded. Place your code within this block:

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

This ensures that your code runs after jQuery initialization.

Additional Considerations

• Verify that your jQuery plugins are loaded after jQuery core. Plugins extend "$," so loading them early can cause issues.
• Consider using document.readyState to separate code that can run without jQuery from code that requires it.

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