Shallow Copy of an Object

extend.js

function extend(a, b) {
  var c = {}, attr;
  for (attr in a) {
    if (Object.prototype.hasOwnProperty.call(a, attr)) {
      c[attr] = a[attr];
    }
  }
  for (attr in b) { 
    if (Object.prototype.hasOwnProperty.call(b, attr)) {
      c[attr] = b[attr]; 
    }
  }
  return c;
}