To me, a method called isNaN should intuitively return false only on numbers and true on everything else. That is exactly what the isNaN() global method does. However, if you're looking to compare a value to NaN (which you cannot do with === or ==), then Number.isNaN is your choice.
For example:
isNaN(' '); // false => because Number(' ') is equal to 0 (a number)isNaN(true); // false => because Number(true) is equal to 1 (a number)
In short, isNaN also tries to perform type conversion. That is why some developers consider it broken.
