Jquery - $ is not defined

javascript

prompt-engineering

best-practices

functions

byAnton Shumikhin·Sep 18, 2024

The error $ is not defined suggests JQuery isn’t charged up when your script gets going. Prioritize including the JQuery script prior to your code:

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script>
  // Code dependent on jQuery: it's time to party! 🎉
  $(function() {
    // Your code unfurls here
  });
</script>

Ensure that JQuery isn't playing hide-and-seek by checking the JQuery src link is operational and no network hurdles are obstructing the load.

Don't get caught in these traps

Before diving deeper into the labyrinth, ensure you haven’t fallen into familiar pitfalls:

Verify the script is loading using your browser development tools; they're not just for pretty console logs!
Plant the jQuery <script> tag above your script tags; it likes to be on top!
Cocoon your jQuery code within the safe $(document).ready(function(){ /* your code here */ });, so it waits patiently till the DOM is ready.

Finding the sweet spot for jQuery

Positioning matters. Like a knight on a chessboard, place your jQuery script tag:

At the finale of the <body> section to speed up page rendering (who doesn't love a fast page load?).
In the HEAD section when it must catch the early bird.

For smoother operations, async or defer might need to sit on the bench if your scripts rely on jQuery. They might get too excited and run before jQuery has had its morning coffee.

Living in harmony with other libraries

If other libraries are trying to steal $'s spotlight:

jQuery.noConflict();
jQuery(document).ready(function($){
  // Now you see $, now you don't!
});

This approach resets $ so jQuery can coexist with other libraries in perfect harmony. Aren't we all about peace, love and understanding?

All aboard the jQuery train

Opt for a CDN but keep a local copy as a safety net:

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script>window.jQuery || document.write('<script src="/path/to/your/local/jquery.min.js"><\/script>')</script>

Like a spare tire for your vehicle, a fallback script ensures the journey continues uninterrupted!

Playing detective with network issues

When faced with a $ is not defined signal, you might be looking at network issues or even a game of hide and seek. Here's how to catch the culprits red-handed using the developer tools:

Ensure the jQuery status code is dressed in a glowing 200 OK.
Check that the MIME type is putting on the text/javascript uniform to avoid identity crisis!

Setting a good example with best practices

Steer the way:

Make sure jQuery has a first-class ticket before plugins board the train.
Avoid being a rebel by editing the core jQuery file or playing tricks with $.
Use a dependable version control to keep the script serving kept in check.

Managing $ in the matrix

Within the realms of inline jQuery code, use this charm:

(function($){
  // In here, $ is the king of the world!  
})(jQuery);

This spell — better known as the Immediately Invoked Function Expression (IIFE) — fosters a safe haven for $, keeping it secure from global conflicts.

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