Add Property to Object that is returned by Sequelize FindOne

Question

I am trying to add a property to a sequelize instance before passing it back to the client.

router.get('/cats/1', function (req, res) {     Cat.findOne({where: {id: 1}})         .then(function (cat) {             // cat exists and looks like {id: 1}             cat.name = "Lincoln";             // console.log of cat is {id: 1, name: Lincoln}             res.json(cat);         }); }); 

The client only see's {id: 1} and not the newly added key.

• What is going on here?
• What type of Object is returned by Sequelize?
• How can I add new properties to my Cats and send them back?

Answer 1

The following works for sequelize v4.

... const order = Order.findOne(criteria); order.setDataValue('additionalProperty', 'some value'); ... 

Hope this helps. It's a bit late but in case people are still looking for answers.

Answer 2

The Sequelize Model class (of which your cats are instances) has a toJSON() method which res.json will presumably use to serialise your cats. The method returns the result of Model#get() (https://github.com/sequelize/sequelize/blob/95adb78a03c16ebdc1e62e80983d1d6a204eed80/lib/model.js#L3610-L3613), which only uses attributes defined on the model. If you want to be able to set the cats name, but not store names in the DB, you can use a virtual column when defining your cat model:

sequelize.define('Cat', {   // [other columns here...]   name: Sequelize.VIRTUAL }); 

Alternatively, if you don't want to add properties to the model definition:

cat = cat.toJSON(); // actually returns a plain object, not a JSON string cat.name = 'Macavity'; res.json(cat);