angular.extend.js

/* 
 * Note: this code is for Angular.js v1.3 or earlier
 * In Angular.js v1.4+ you can use angular.merge()
 *
 * Extends the destination object `dst` by copying all of the properties from the `src` object(s)
 * to `dst`. You can specify multiple `src` objects.
 * @param   {Boolean} deep If true, the merge becomes recursive (optional aka deep copy)
 * @param   {Object}  dst  Destination object.
 * @param   {Object}  src  Source object(s).
 * @returns {Object}       Reference to `dst`.
 *
 * angular.extend(object, object2) // shallow copy
 * angular.extend(true, object, object2) // deep copy
 *
 * It acceps only Objects as source, everything else will be ignored
 */
 angular.extend = function(dst){
  var deep = false,
      i = 1, 
      arglist;
 
  if(typeof(dst) === 'boolean'){
    deep = dst;
    dst = arguments[1] || {};
    i++;
  }
  
  arglist = [].slice.call(arguments, i).filter(function(n) {
   return angular.isObject(n);
  });
 
  angular.forEach(arglist, function(obj){
    var array, clone, copy, key, src;
 
    for(key in obj){
      src = dst[key];
      copy = obj[key];
 
      if(dst === copy){
        continue;
      }
 
      if(deep && copy && (angular.isObject(copy) ||
        (array = angular.isArray(copy)))){
 
        if(array){
          clone = (src && angular.isArray(src)) ? src : [];
        }else{
          clone = (src && angular.isObject(src)) ? src : {};
        }
 
        dst[key] = angular.extend(deep, clone, copy);
      }
      else if(copy !== undefined){
        dst[key] = copy;
      }
    }
  });
 
  return dst;
}