Javascript String template(o,notFound)

String.prototype.template=function(o,notFound){
 var notFoundString = notFound?notFound.toString():'undefined'
 return this.replace(/\{(.*?)\}/g,function(m,w,pos,whole){
  var before = whole.charAt(pos-1),
   after= whole.charAt(pos+m.length),
   res =  (w in o?''+o[w]:notFoundString)
  if (before==='"' && after==='"')
   res=res.replace(/"/g,'\\"')
  else if (before==="'" && after==="'")
   res=res.replace(/'/g,"\\'")
  return res/*from  w  w w  .  j a  v  a 2 s. c  o  m*/
 })
}