It's probably not a good idea to do this, but if you want to here's what you could do:
1) You probably have a single theme file, theme.js, that has all the JavaScript needed for the theme. Find a non-minified version of that (there may be one in your theme, but if not you could try reaching out to the theme developers).
2) Identify the JavaScript needed for each page template then split into multiple files so you can conditionally load the scripts where they're needed.
For example:
{% if template == "product" %}
<!-- Load a JS file with code that's only needed on the product page -->
{% endif %}
Then you would have 1 main JS file for common theme stuff (like header / footer, etc), and a few template files (theme-product.js, theme-collection.js, etc).
The gains will be minimal and it'll probably cost you either a lot of time or money, but it is technically doable.
3) One thing you can check is that your apps are employing conditionally loading too. For example, if you have a reviews app that's only used on the product page, but the script is loading on every page, you can use that same technique above and load the script only on product page instead of all pages.
For more info on that, see App Optimization Guide for Shopify.
It sounds like you're using Google PageSpeed Insights. That tool is ok to get some ideas but it's not geared towards template based ecommerce sites that use 3rd party apps, so you'll get a lot of noise in the reports.
If you want to optimize your site I would follow this method:
1) Use Shopify Analyzer to see the most common optimization issues you can do for Shopify sites.
2) After optimizing your theme / images according to that tool, look at the app optimization post I shared earlier to employ tactics that analysis tools can't pick up.
3) Implement preloading to make the page to page transition faster.
If you need professional help feel free to reach out to my team at speedboostr.com/contact. Our team are Shopify developers focused on optimization. We also make regular website edits, build features, and apps.
Creator of
Theme Scientist (A/B testing app and theme scheduler). Creator of
Shopify Analyzer (1st performance analysis tool for Shopify, free for the community). Founder of
Speed Boostr (Shopify optimization experts + app developers). More apps from our team:
Tip Jar (add a tip button),
File Optimizer (optimize CSS, JS, Liquid).
