javascript问题

保存一下我的javascript学习代码

var urlg = /(\w+):\/\/([\w.]+)\/(\S*)/gi;
var url = /(\w+):\/\/([\w.]+)\/(\S*)/i;

var text = "Visit my blog at http://www.example.com/~david ,,,Visit my blog at http://www.example.com/~david";

var result = text.match(urlg);

if (result != null)

{
 for(var i in result)//这个遍历方法。。。如果result是个数组会访问到数组每个元素，但数组长度小于对象属性数就会访问到对象的属性？？？
//在这做个记号以后研究。或者有知道的告诉我一下~
 {
  if (result[i] == null||result[i]==undefined)
  {
   continue;
  }
alert(i+'a'+result[i]);
  var currentM  = result[i].match(url);
  alert('currentM:'+currentM);
  if (currentM == null||currentM==undefined)

  {
   alert('a');
   continue;
  }
//使用了match后匹配的内容会放到公有对象RegExp中
//如下
  var fullurl = RegExp.$1;//currentM[0]; // Contains "http://www.example.com/~david"

  var protocol = RegExp.$2;//currentM[1]; // Contains "http"

  var host = RegExp.$3;//currentM[2]; // Contains "www.example.com"

  var path = RegExp.$4;//currentM[3]; // Contains "~david"
  alert(fullurl+'&'+protocol+'&'+host+'&' + path)
 }
}