Calculator with History

Code Feedback
1

I recently finished my first main project with javascript with this calculator. I decided to include a saved history of inputs which provided an interesting challenge.

I was wondering what you guys thought about how I organised my javascript code and if you found any bugs.

https://codepen.io/Chalkhous/pen/MNEOmV?editors=0010

1 Like
2

Hey @Chalkhous, it looks really great, nice work! Unfortunately, almost every case I thought might produce a bug was positive. I think it’s a good example of difference between MVP/prototype and production-level page/app. It’s relatively easy project and most importantly it involves numbers, so I would suggest you to challenge yourself even further and try to polish it to a production-level thing, believe me you will learn A LOT and will be amazed how much more work shall be done here! Knowing how to deal with numbers is a good skill!
Let me know if you’d like to go further with the challenge and I’ll suggest you couple tests you shall complete for your calculator! :wink:

3

Hey, thanks for the feedback! Could you give a few examples of the bugs you found? I tried my best to get rid of them so I’m not sure on the best way to test it.

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I’ll separate test cases to families and will go from most popular to least popular (and I won’t include those that you covered)
1. Edge cases
1A. How do deal with limit of digits on the screen?

  • 99999999999 + 1 should be equal to 100000000000
  • 10000000000 - 0.125 should be equal to 9999999999.875

1B. Do you allow unlimited chain of operations? If yes, how are you going to represent it in history?

  • 1 * 1 * 1 * 1 * 1 * 1 * 1 * 1 * 1 * 4 should be equal 4

2. Misuse
2A. User expect sign % to calculate percentage and not modulo

  • 45% should be equal to 0.45

2B. User must be able to start floating point number with .

  • 45 + .45 should be equal 45.45

2C. User expects CE (Clear entry) to clear entry. Consider ← sign instead.

3. Numbers and math
3A. Bit truncation (classic)

  • 0.1 + 0.2 should be equal to 0.3

3B. Division by 0 (classic) - any attempt shall be resolved in Error

  • 2 / 0 = + 2 should throw/output an Error

4. Accessibility
4A. User shall be able to use calculator with keyboard input

1 Like
5

Thanks for taking your time to write all that up! I don’t think I would have thought of any of those cases.
Is 3b necessarily wrong though with 2 / 0 = infinity?

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It’s not specifically wrong, as you’re developer and it’s your call at the end. But Infinity + 2 should not equal to 2 - that’s for sure! :wink:

  • Basically Infinity in your case should act as Error and only C/CE should be allowed afterwards.
7

Ah I see, I misunderstood. That 0.1 + 0.2 case is interesting as well.