Deployed to Vercel: (Welcome test!) https://react-project-01-calculator.vercel.app/
1. Can only perform operations between 0 and 9 (1+1), cannot perform operations like tens or hundreds (11+1) .
2. Allowed two operations signal input like ++ //, and result in errors after clicking = .
3. Fixed errors when input text is empty
4. Fixed errors when clicking = with empty input text or ended with operation signals.
5. Adjusted CSS when result have multiple digits out of the container
1. Added CSS when hovering buttons
2. Added function 'Back' to undo the last input
1. ReactJS Tutorial - Build a Calculator App from Scratch
https://www.youtube.com/watch?v=n_cKSILMzmM
2. math.js library
https://mathjs.org/index.html