网页http://www.club-emb.info/2018/出现Uncaught ReferenceError: jQuery未定义错误求助

Hey there, let's break down why you might still be hitting this error even when you've tried loading jQuery first. Here are the most common fixes to check:

• Verify jQuery actually loads successfully
  Open your browser's DevTools (F12) and head to the Network tab. Reload the page and look for your jQuery script file. If it shows a 404 status, your file path is incorrect—double-check the URL (whether it's a local file or CDN link). For a reliable fallback, you can use a well-maintained CDN link like:

  <script src="https://code.jquery.com/jquery-3.7.1.min.js"></script>
  

• Check for async/defer attributes causing race conditions
  If your jQuery script tag uses async or defer, the browser loads it in the background without blocking subsequent scripts. That means your code relying on jQuery might run before jQuery finishes loading. Remove those attributes, or wrap your dependent code in a ready handler to ensure it runs only after jQuery is available:

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

• Confirm script execution order in your HTML
  Even if you think jQuery is first, double-check the actual order of <script> tags in your DOM. Any script that uses jQuery must come after the jQuery script tag. For example:

  <!-- Correct order -->
  <script src="jquery.js"></script>
  <script src="script-that-uses-jquery.js"></script>
  

• Clear browser cache or force a fresh load
  Sometimes browsers cache old versions of your page (or a broken jQuery file). Try a hard refresh (Ctrl+Shift+R on Windows/Linux, Cmd+Shift+R on Mac) to bypass cache. You can also add a version parameter to your jQuery URL to force a reload:

  <script src="jquery.js?v=20240520"></script>
  

• Check for variable conflicts
  Other scripts might overwrite the $ or jQuery global variables (common with libraries like Prototype). Test replacing $ with jQuery in your code to see if the error goes away. If that works, you can use jQuery.noConflict() to resolve the conflict:

  var $j = jQuery.noConflict();
  $j(document).ready(function() {
    $j("#element").doSomething();
  });
  

Hope one of these fixes gets your jQuery working properly!

内容的提问来源于stack exchange，提问作者Roman Hricišin