The Problem: Your JavaScript external script, main.js, is not executing when included in the <head> section of your HTML, while an inline script containing the same code works correctly in the <body>. This indicates a timing issue related to the order of script execution and the DOM’s readiness.
Understanding the “Why” (The Root Cause):
The <head> section of your HTML document is parsed before the <body> content. When you place your <script src="..."> tag in the <head>, the browser begins loading main.js immediately. However, if your script uses jQuery to manipulate elements on the page (like your .highlight class), it may attempt to execute before these elements have been fully loaded and added to the DOM (Document Object Model). This causes the jQuery selectors to return nothing, preventing your animation from running. In contrast, your inline script in the <body> works because it executes after the page’s elements have been parsed and the DOM is ready.
Step-by-Step Guide:
Step 1: Relocate the <script> tag. The most straightforward solution is to move your <script> tag including the external main.js file from the <head> section to just before the closing </body> tag (</body>). This ensures that the script executes after the entire page’s DOM content has been fully parsed and loaded.
<!DOCTYPE html>
<html>
<head>
<title>My Webpage</title>
<!-- Other head content -->
</head>
<body>
<!-- Your HTML content here -->
<script src="assets/scripts/effects/main.js" charset="utf-8"></script>
</body>
</html>
Step 2: (Alternative) Use $(window).load(). If you absolutely must keep your external script in the <head>, you can modify your main.js to use jQuery’s $(window).load() function instead of $(document).ready(). $(window).load() waits for all page elements and resources, including images, to finish loading before executing the enclosed code.
Before (in main.js):
$(document).ready(function() {
$(".highlight").animate({width: "50%"}, 3000);
});
After (in main.js):
$(window).load(function() {
$(".highlight").animate({width: "50%"}, 3000);
});
Step 3: Verify your file path and code. Double-check that the path to your main.js file (assets/scripts/effects/main.js) is correct relative to your HTML file. Also, ensure that the contents of your external main.js are identical to the code you’ve successfully tested inline. Slight differences in whitespace or encoding can cause errors. Use your browser’s developer tools (usually accessed by pressing F12) to examine the Network tab and confirm that main.js is being loaded without errors (a 404 error indicates a file path problem).
Common Pitfalls & What to Check Next:
- Caching: Your browser might be caching an older version of
main.js. Try adding a cache-busting parameter to your <script> tag, like main.js?v=1.0, and increment the version number (v=1.1, v=1.2, etc.) each time you make changes to the script.
- JavaScript Errors: Check your browser’s console for any JavaScript errors reported. These error messages often pinpoint the exact problem within your script.
- jQuery Conflicts: If you are using multiple JavaScript libraries that include jQuery, ensure there are no conflicts between them. This is less likely in this case but it’s always a good practice to check.
Still running into issues? Share your (sanitized) config files, the exact command you ran, and any other relevant details. The community is here to help!