AI solution for JavaScript Quiz on BFE.dev
109. isNaN()

The code outputs the following by console.log:

true
false
true
true

Explanation:

• Number.isNaN(a) returns true because a is a string and cannot be converted to a number.
• Number.isNaN(b) returns false because b is a number and is not NaN (Not a Number).
• isNaN(a) returns true because a is a string and cannot be converted to a number, so it is considered NaN.
• isNaN(b) returns true because b is a number, but NaN is a special value of number type.