Check for NaN, null and >=0 in one condition

Question

I have a var a;

Its value can be NaN, null and any +ve/-ve number including 0.

I require a condition which filters out all the values of a such that

Answer 1

My best solution to filter those values out would be with 2 condition and it is like;

 if(a!=undefined && a>=0){
      console.log('My variable is filtered out.')
    }

I am not sure but there is no single condition usage to make it.