How to combine local changes with git type without additional commit?

I hid my changes to work on another task. When I finished another task, I resumed work on the modifications that I hid, except that I forgot them first pop. Now I partially completed the work of both local modifications and in git stash. When I try to combine them using git stash pop, I get the following error:

error: Your local changes to the following files would be overwritten by merge:
    file.js
Please, commit your changes or stash them before you can merge.
Aborting

I would like git to merge the folded changes locally before committing. I tried to look for a solution a bit, but still did not understand.

Your help is much appreciated!