get capture in global regexp matching

re.dms

re = new RegExp('a(.)','g');
a = 'akgatranavayakhahjajatdaa';
//b = re.exec(a);
//for(i in b)alert(????);

var results = [ ];
a.replace (re, function (s, p1) {
  results.push ([ s, p1 ]);
  return '';
});

var t = [ ];
for (var i = 0; i < results.length; ++i) {
  var r = results [i];
  t.push ('$0=' + r [0] + ', $1=' + r [1]);
}
alert (t.join ("\n"));