If you are developing a website or customizing a Blogger template and see 'Uncaught ReferenceError: $ is not defined' in your browser console, you are not alone. This error occurs when your JavaScript code attempts to use jQuery (referenced by the $ shortcut) before the library has been properly loaded or recognized by the browser.
Step 1: Verify the jQuery Library Link
The most common cause is a missing script tag. You must include the jQuery library in your HTML before calling any jQuery functions. Add the following line inside your <head> tag or just before the closing </body> tag:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
Step 2: Check the Script Execution Order
Browsers execute scripts in the order they appear. If your custom JavaScript file or inline script is placed above the jQuery library link, the browser won't know what $ means yet. Always ensure the jQuery CDN link is placed ABOVE your custom scripts.
Step 3: Solve Blogger Template Issues (Async/Defer)
In many modern Blogger templates, scripts are set to load asynchronously for speed (using async='async'). This can cause your custom code to run before jQuery finishes downloading. To fix this, remove the async attribute from the jQuery script tag or wrap your custom code in a window.onload function to ensure all assets are ready.
Step 4: Use jQuery.noConflict() Mode
If you are using other libraries (like Prototype or MooTools) that also use the $ sign, a conflict occurs. You can resolve this by using jQuery instead of $, or by wrapping your code in an Immediately Invoked Function Expression (IIFE) like this:
(function($) {
// Your code using $ goes here
})(jQuery);
Step 5: Fix Protocol Mismatch (HTTP vs HTTPS)
If your website is hosted on a secure server (HTTPS), but your jQuery link starts with http://, the browser will block the script due to "Mixed Content" security policies. Always use https:// in your source URLs to ensure the library loads correctly across all environments.
Step 6: Check for Typos and Network Blocks
Ensure there are no typos in your script tag and check if your network (or a browser extension like an ad-blocker) is blocking public CDNs. If the CDN is down, you can host the jquery.min.js file locally on your own server for better reliability.
💡 Pro Tip: Keep your software updated to avoid these issues in the future.
Category: #Website