Woocommerce 3.2.6更新后jQuery无法加载问题排查求助

Let's break down the exact causes behind your jQuery failure, which is triggering the broken images and non-functional buttons:

1. Mixed Content Blocking from Protocol-Relative URLs #

Your jQuery URL uses a protocol-relative format (//ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js). While this should automatically use HTTPS if your site is served over HTTPS, there are a few scenarios where this fails:

• If your server or a plugin incorrectly handles the site's protocol (e.g., forcing HTTP in backend settings while the frontend uses HTTPS), browsers will try to load jQuery over HTTP. Modern browsers block HTTP resources on HTTPS pages (mixed content) as a security measure, so jQuery gets blocked entirely.
• Some older server configurations or CDN setups don't properly resolve protocol-relative URLs for HTTPS sites, leading to failed requests.

2. The defer Attribute Causing Execution Order Issues #

The defer attribute tells the browser to load the script in the background and only execute it after the DOM is fully parsed. This creates two critical problems here:

• The immediately following jQuery.noConflict() code runs before jQuery has finished loading (since defer delays execution). This throws an error because jQuery isn't defined yet, breaking any subsequent code that relies on jQuery.
• Most WordPress themes and plugins assume jQuery is loaded synchronously (available immediately when their scripts run). When jQuery is deferred, dependent scripts fire first and can't find the jQuery object, leading to broken functionality like unloaded images and non-working buttons.

3. Compatibility Conflict Between Old WordPress and WooCommerce #

WordPress 4.9.1 is a fairly outdated version, and updating WooCommerce to 3.2.6 introduces changes to how scripts are enqueued. WooCommerce 3.x revised its script loading logic to align with newer WordPress standards, but this can clash with the older WordPress 4.9.1's script handling:

• WooCommerce might be overriding or modifying the default jQuery enqueue settings (like adding the defer attribute) that WordPress 4.9.1 doesn't handle correctly.
• The older WordPress core might not properly validate protocol-relative URLs when paired with WooCommerce's updated script enqueuing methods.

4. Theme/Plugin Conflict Modifying jQuery Loading #

It's also possible that a custom theme or another active plugin is altering jQuery's load parameters:

• Some performance plugins add defer attributes to scripts to speed up load times, but this can conflict with WooCommerce's script dependencies after the update.
• Your theme might have custom code that modifies the jQuery URL or attributes, and the WooCommerce update disrupted this logic, leading to the missing HTTPS: prefix and incorrect defer flag.

内容的提问来源于stack exchange，提问作者Jethro Hazelhurst