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

I had the same problem some weeks ago, I solved it with:

if(~~Number(test1)>0) {
  //...
}

http://jsfiddle.net/pT7pp/2/