function defaults(object) {
	      if (object == null) {
	        return object;
	      }
	      var args = arrayCopy(arguments);
	      args.push(assignDefaults);
	      return assign.apply(undefined, args);
	    }
Assigns own enumerable properties of source object(s) to the destination
object for all destination properties that resolve to `undefined`. Once a
property is set, additional defaults of the same property are ignored.

@static
@memberOf _
@category Object
@param {Object} object The destination object.
@param {...Object} [sources] The source objects.
@returns {Object} Returns `object`.
@example

_.defaults({ 'user': 'barney' }, { 'age': 36 }, { 'user': 'fred' });
// => { 'user': 'barney', 'age': 36 }