A simple and naive extend implementation

extend.js

function extend(obj, extend){ 
  var p;
  for (p in extend) {
    obj[p] = extend[p];
  }
  return obj;
}

var obj = {
  a : 1
, b : 2
, c : 3
}

var ext = {
  a : 4
, b : 5
}

extend(obj, ext)
// { a: 4, b: 5, c: 3 }
obj = extend(obj, ext)
// { a: 4, b: 5, c: 3 }