Why NaN is greater than any number in JavaScript? [duplicate]

Question

Here is an example:

parseInt(50) > parseInt('a');

When executing this on a console, it will return false. My original code looks somewhat like this:

variableB = parseInt(jQuery('some-element').html());
if(parseInt(variableA) > variableB)
     // do something
else
     // do something else

Sometimes the some-element will not be filled and thus return NaN. When this happens, I do want the else block to be executed. I am actually getting what I expect, but I just want to make sure that it indeed is intended to work this way.

Answer 1

In IEEE 754 arithmethic, the floating-point model used by JavaScript, NaN (or not-a-number) is, by definition, not less than, equal to, or greater than any other number.

Notice that this even applies to two NaNs: if x = NaN and y = NaN, the comparison x === y will return false.

Below I quote the portion of the IEEE 754 Standard (Section 5.11) where this behavior is specified:

Four mutually exclusive relations are possible: less than, equal, greater than, and unordered. The last case arises when at least one operand is NaN. Every NaN shall compare unordered with everything, including itself.

Answer 2

All comparisons involving NaN will always return false.
NaN is neither less than nor greater than any number.