For your customerValidation function, I would prefer to write my function validating the fields separately. All fields are required but the name is checked only if the login is checked only if the email is checked. I don't think the ternary operator is appropriate for this usecase.
For validation, I would actually use something like Joi.
This is a problem with contrived examples. You think of a technique you want to demonstrate, then you find an example that will demonstrate it. Most times, there are better ways to solve the example you used. But those other ways, do not demonstrate the technique you wanted to demonstrate.
My goal was to demonstrate the ternary, not to show input validation.
I probably should have used some obscure cat example. Something I need to work on for sure.
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