function diff(a, b)
{
    if (a == null || b == null)
        return 0;
    else
        return Math.max(a - b, 0);
}
// get the natural difference between a and b
get the natural difference between a and b
get the natural difference between a and b
function diff(a, b)
{
    if (a == null || b == null)
        return 0;
    else
        return Math.max(a - b, 0);
}
function diff ( a , b ) { if ( a == null || b == null ) return 0 ; else return Math . max ( a - b , 0 ) ; }
get the natural difference between a and b
get the natural difference between a and b