'How to fix my old react project not working as expected?

I'm new to react and have just added some regex validation to a jsx file in an existing react project (created about 4 months ago) . After building a new bundle.js file my react project works completely differently. I'm pretty sure the code is correct and hasn't broken anything. I tried to run the older working version of the project without my changes locally and it still works differently. I think this might be because of build issues. What configurations can I do to make the react app work as expected like it was before?



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