Is NaN equal to NaN?

Question

parseFloat(\"NaN\")

returns \"NaN\", but

parseFloat(\"NaN\") == \"NaN\"

returns false. Now, that\'s probably a go

Answer 1

isNaN works for all values that aren't numbers

isNaN('foo') == true
isNaN(NaN) == true
isNaN(12) == false
isNaN([1,2,3]) == true

If, however you want to check for NaN specifically, or avoid type coercion;
you can use Number.isNaN instead

Number.isNaN('foo') == false
Number.isNaN(NaN) == true
Number.isNaN(12) == false
Number.isNaN([1,2,3]) == false