docs: function extend(destination, source) {
      // Chrome < 14 incorrectly sets `destination` to `undefined` when we `delete arguments[0]`
      // http://code.google.com/p/v8/issues/detail?id=839
      var result = destination;
      delete arguments[0];
  
      forEach(arguments, function(source) {
        forProps(source, function(value, key) {
          result[key] = value;
        });
      });
      return result;
    }