when i use d3.color parse `rgba(255,255,255,0)`, the result of `r`,`g`,`b` is NaN. why the `a` is 0, the `r`,`g`,`b` is NaN.
when i use d3.color parse
rgba(255,255,255,0), the result ofr,g,bis NaN.why the
ais 0, ther,g,bis NaN.