_.each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
    var method = ArrayProto[name];
    _.prototype[name] = function() {
      var obj = this._wrapped;
      method.apply(obj, arguments);
      // TODO why ? 
      if ((name === 'shift' || name === 'splice') && obj.length === 0) delete obj[0];
      return chainResult(this, obj);
    };
  });