feat(isUPC): add validation for UPC code which is Universal Product Code widely used worldwide for …

[rahulnikam2002]

What i have done?

• Added a validation for UPC code.
• Tested on with valid and invalid inputs

Why i have done?

• UPC codes are essential for modern retail operations and are used in inventory control and price comparison.
• helps to maintain accurate pricing information and streamline inventory management.

References

• https://www.shopify.com/blog/what-is-a-universal-product-code#:~:text=The%20purpose%20of%20UPCs%20is,checkout%20process%20at%20grocery%20stores.

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)

[WikiRik]

I'm not so sure if this is an useful addition to the project. The check is simple, just if its 12 digits. I also did not see any other requests for this to be added. But I'm open to hear what others/maintainers think

[rahulnikam2002]

okay @WikiRik, will try to add more useful features!

I'm not so sure if this is an useful addition to the project. The check is simple, just if its 12 digits. I also did not see any other requests for this to be added. But I'm open to hear what others/maintainers think

[laserguru]

@rahulnikam2002 @WikiRik
Bumping this because I need this feature and the feature pretty much was already there

Turns out two things happen:

• It is not just a simple check, there's a calculation to see if it is really valid
• We already (mostly) have the feature in the form of isEAN, because the calculation is the same

EAN codes are a superset of UPC. But a 12 digit UPC, by itself, is not a valid EAN-13.
But add a zero in front, and it is! (And that's the specification, not a hack)
UPCs as such are only assigned in the USA and Canada, and EANs elsewhere.
At the moment, I simply changed my code to prepend the zero if the code is 12 digits long:
isEAN(code.length === 12 ? "0" + code : code)
Checked with a bunch of items with UPCs and it validates correctly.

Will follow up with a pull request once I make the changes to the validator.js source. Now, should this be part of isEAN or a separate isUPC?