Explain please ^_^

Question

Why NaN, isn't suppose to be undefined?
https://code.sololearn.com/WqB7lKZq10jv/?ref=app

Answer 1

Because JavaScript in operations cast automatically the not defined or the var type , and in your case the last variable it's not a number

Answer 2

z is defined as a var but not initialized so your code will never throw undefined
and NaN (not a number ) is usually indicate an error condition for a function that should return a valid number

Answer 3

Why So Serious ? It's because of result 30undefined as string?Means NaN? Because string converts to NaN when math operations is executed, right?

Answer 4

In very simple language, i will ask you , where is z kid

https://code.sololearn.com/W3vok4QcCpId/?ref=app

Answer 5

😵PSYCHØ CØDER😵 I understand, but it's doesn't answer me at all. Number*Number*undefined means NaN. I didn't get it.