code: function pick(obj) {
    var copy = {};
    var keys = Array.prototype.concat.apply(Array.prototype, Array.prototype.slice.call(arguments, 1));
    forEach(keys, function(key) {
      if (key in obj) copy[key] = obj[key];
    });
    return copy;
  }
docs: extracted from underscore.js Return a copy of the object only containing the whitelisted properties.