javascript - Why isNaN(123) test result is false, is the input value not a number?

Question

isNaN(123)；//false
isNaN('123');//false

Answer 1

NaN refers to Not-a-Number, isNaN(), if it is NaN, it returns true.
Then 123 is not NaN, of course it returns false.
'123' is type converted to Number type 123, so it returns false.

Answer 2

Answer 3

This is to judge whether it is NaNthis special number....