js的优化后的replace函数

 <script language="JavaScript">

 function Replace(replaceStr , oldchar , newchar , flag)
 {
  if(typeof(flag)=="undefined") flag = "g" ;
  var re = new RegExp(oldchar,[flag]) ;
  return replaceStr.replace(re,newchar);
 }
 alert(Replace("abcdeAbcdef",'a','777','ig'));

 </script>