How to use async.map

I am having two for loops. One nested in another. I want to iterate on a single Object and change a property in it with another value, something like this:

for(i=0;i<items.length;<i++){
 obj.changeThisAttribute = "abc";
  for(j=0;j<items.anotherobj.length;j++){
   items.anotherobj.changeThisAttribute = "dyz";
  }
}
return items;

Is there any better way of doing this? I have read about Async.map and think that it will be a good solution however there is no good example of the same. Please suggest a running example or any alternative way of achieving this.