It should work, if you create an empty js file in the code editor in your assets folder and than copy and paste the contents of your js file.
- Go to your shopify code editor
- Go to assets
- Create a js file
- Take your original js file, open it, copy the content
- Back to your shopify code editor
- Paste the content
- Have fun
Sorry mate, of course this should also work, if you upload it in the code editor. My bad.