Get mongoose schema fields, excluding specified values, for lodash.

pick-schema.js

_.mixin({ pickSchema: function (model, excluded) {
    var fields = [];
    model.schema.eachPath(function (path) {
      _.isArray(excluded) ? excluded.indexOf(path) < 0 ? fields.push(path) : false : path === excluded ? false : fields.push(path);
    });
    return fields;
  }
});

// Example
var UserSchema = new Schema({
  fName: String,
  lName:   String,
  comments: [{ body: String, date: Date }],
  date: { type: Date, default: Date.now },
  hidden: Boolean,
  meta: {
    votes: Number,
    favs:  Number
  },
  createdAt: { type: Date, required: true, default: Date.now }
});

var User = mongoose.model('User', UserSchema);

_.pickSchema(User); //  all schema fields
_.pickSchema(User, '_id'); //  all except _id
_.pickSchema(User, ['_id', 'meta.votes', 'hidden']); // result ['fName', 'lName', 'comments', 'date', 'meta.favs', 'createdAt']

// usage example: filter req.body data, and get only neccessary fields
_.pick(req.body, _.pickSchema(User, ['_id', 'createdAt', 'hidden']))