How to Fix Javascript Errors in WordPress

Introduction

Javascript Errors in WordPress can break menus, forms, sliders, and even entire checkout flows with no obvious clue on the page itself. All you see is “nothing works” while your visitors quietly leave.

When Javascript Errors appear, they often look mysterious, but in reality almost every issue comes from a specific script, plugin conflict, or caching rule that you can track down step by step.

This guide focuses on fixing Javascript Errors in WordPress without guesswork. You will learn how to confirm that a problem is JavaScript related, read the browser console, safely enable WordPress debugging, track down bad plugins or themes, and fix or replace the scripts causing Javascript Errors without wrecking your live site.

What You Need to Start

• Access to your WordPress admin dashboard.
• Access to your hosting File Manager or an FTP/SFTP client.
• A recent full site backup before changing code or core files.
• A modern browser such as Chrome, Firefox, or Edge.

If you do not have a recent backup, schedule one first using your hosting tools or a backup plugin. For a step by step walkthrough, see Beginner guide to WordPress speed optimization so you are protected while fixing Javascript Errors.

Step 1: Identify Javascript Errors in your browser console

Before you try to fix anything, you must confirm that the issue is caused by JavaScript and capture the exact error message. That message will tell you which file and line are breaking your site and producing those Javascript Errors.

1. Open the broken page in Chrome (or another modern browser).
2. Press Ctrl + Shift + I (Windows) or Cmd + Option + I (Mac) to open Developer Tools.
3. Click the Console tab at the top of the developer tools panel.
4. Reload the page while the Console is open and look for red error messages such as Uncaught TypeError or ReferenceError jQuery is not defined. These are classic Javascript Errors that stop the rest of your scripts from running.
5. Copy the full error text and file path shown in the console into a note for later reference so you can match them to specific Javascript Errors on the site.

For a deeper walkthrough, you can also follow the official WordPress guide Using Your Browser to Diagnose JavaScript Errors.

Step 2: Enable WordPress debugging for scripts

The console tells you what is failing in the browser. WordPress debug settings can show you PHP notices, script loading issues, and log errors that happen before the page is fully rendered. This makes it easier to connect specific warnings in the logs to the Javascript Errors you see in the browser.

1. Log in to your hosting account and open the File Manager, or connect via FTP/SFTP.
2. Navigate to your WordPress installation directory (usually the folder that contains wp-admin and wp-content).
3. Locate the file named wp-config.php and download a backup copy to your computer.
4. Edit wp-config.php in a plain text editor (not Word or Pages).
5. Just above the line that says That’s all, stop editing, add or update the following constants:

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );
define( 'SCRIPT_DEBUG', true );

Save the file and upload it back to your server, overwriting the existing wp-config.php file.

Visit the broken page again, refresh your browser, and then open wp-content/debug.log to see if there are warnings or errors related to script loading or specific plugins. Often you will see log entries that line up with the Javascript Errors from your console.

Step 3: Isolate plugin conflicts causing Javascript Errors

Most WordPress Javascript Errors come from plugins that load conflicting scripts, outdated libraries, or duplicate versions of jQuery and other dependencies. The fastest way to confirm a plugin conflict is to temporarily disable non-essential plugins and watch whether the Javascript Errors disappear.

1. Log in to your WordPress admin and go to Plugins → Installed Plugins.
2. If possible, put your site into maintenance mode or switch to a staging copy first. For a safe workflow, see How to use ai in WordPress.
3. Tick the checkbox at the top of the plugin list to select all non-essential plugins, choose Deactivate from the Bulk Actions dropdown, and click Apply.
4. Open the problem page in a new tab, refresh, and check the browser Console again.
5. If the Javascript Errors are gone, go back to Plugins and start reactivating plugins one at a time.
6. After activating each plugin, refresh the front-end page and watch the console. The moment the Javascript Errors reappear, the last plugin you activated is very likely the cause.
7. Leave the problematic plugin deactivated, then contact the plugin developer with your console and debug log messages, or look for a better-coded alternative plugin.

When you identify a problematic plugin, it is also a good time to review whether you still need it. To audit plugin impact more broadly, see How to check if WordPress plugins are up and reduce future Javascript Errors.

Step 4: Test your theme and child theme scripts

If disabling plugins does not fix the Javascript Errors, your theme may be loading scripts incorrectly or conflicting with the version of WordPress you are running. A quick test with a default theme will confirm whether theme code is behind your Javascript Errors.

1. Go to Appearance → Themes in your WordPress dashboard.
2. Note which theme is currently active so you can switch back later.
3. Activate a default theme such as Twenty Twenty Five or another recent default theme.
4. Reload the problem page on the front end and check the Console again.
5. If the Javascript Errors disappear with the default theme, the issue lies in your previous theme or its child theme scripts.
6. Switch back to your original theme and contact the theme developer with the console error details, or proceed to the next step if you are comfortable editing theme code to eliminate Javascript Errors.

Step 5: Check caching, CDN, and script optimization settings

Caching and speed plugins often minify, combine, or defer JavaScript files. A small misconfiguration there can easily produce hard to track Javascript Errors, especially when combined with aggressive CDN rules.

Many of these tools are tied to a CDN (Content Delivery Network). Different CDN setups behave differently with JavaScript and HTML caching, so it helps to know what you are using when troubleshooting Javascript Errors:

1. In your dashboard, open each caching or performance plugin settings page you are using.
2. Look for options referring to JavaScript, such as Minify JavaScript, Combine JavaScript files, or Defer JavaScript.
3. Temporarily disable those JavaScript optimization features while leaving basic page caching enabled.
4. Click the plugin’s Save or Apply button, then use its Clear Cache or Purge All feature.
5. If you use a CDN like Cloudflare, log into that dashboard and purge the cache there as well.
6. Refresh the affected page and check the Console. If the Javascript Errors are gone, turn JavaScript optimizations back on one setting at a time.
7. When the error reappears, use the plugin’s “exclude” or “do not optimize” list to exclude the specific script files mentioned in the console from minification or deferral and stop those Javascript Errors.

For more careful guidance on these options without breaking your layout, see Debugging in WordPress along with your caching plugin’s documentation. This combination of cache tuning and CDN rules is often enough to stop stubborn Javascript Errors.

Step 6: Fix broken Javascript code safely in WordPress

If you have narrowed the problem down to your own custom code or a child theme, you can fix how scripts are loaded and how they use libraries like jQuery. Cleaning up how you enqueue and write scripts is the most reliable way to prevent Javascript Errors from returning.

1. If you do not already have one, create and activate a child theme for your site so you can safely override scripts.
2. Open the child theme’s functions.php file in a code editor via SFTP or your hosting file manager.
3. Add or update your script loading code so it uses wp_enqueue_script() correctly and loads jQuery from WordPress itself instead of from a random CDN.

function mytheme_enqueue_scripts() {
    // Always load WordPress's bundled jQuery
    wp_enqueue_script( 'jquery' );

    // Load your custom script that depends on jQuery
    wp_enqueue_script(
        'mytheme-custom-js',
        get_stylesheet_directory_uri() . '/assets/js/custom.js',
        array( 'jquery' ), // dependency
        '1.0.0',
        true // load in footer
    );
}
add_action( 'wp_enqueue_scripts', 'mytheme_enqueue_scripts' );

If your console shows errors like jQuery is not defined, the code inside your script may be running before jQuery is ready or using $ without wrapping it in a safe scope. Fixing that pattern can clear a whole chain of Javascript Errors at once.

jQuery(function($) {
    // Your code can safely use $ here
    $('.menu-toggle').on('click', function() {
        $('.main-menu').toggleClass('is-open');
    });
});

Upload the updated files, refresh your site, and watch the console again. If the red error messages disappear and your menus or forms behave normally, you have successfully fixed the Javascript Errors in your theme or custom code. For more advanced developers, the official wp_enqueue_script reference is worth bookmarking.

Conclusion You Are Ready to Go

Javascript Errors in WordPress feel scary when everything looks fine on the surface but nothing works when you click. By checking the browser console, enabling safe WordPress debugging, isolating plugins and themes, tuning caching and CDN options, and cleaning up your own script loading, you can turn those mysterious Javascript Errors into clear, fixable tasks.

Once your site is stable again, remember to set WP_DEBUG back to false in wp-config.php so visitors do not see debug details and your log files do not grow forever. Build a habit of testing big changes on a staging site first so future Javascript Errors are caught long before customers notice them.

Further Reading

• Common WordPress backup errors and how to fix
• Common WordPress backup errors and how to fix
• Beginner WordPress security best practices guide
• Beginner checklist optimizing WordPress blog posts
• How to use ai in WordPress

Frequently Asked Questions