Can I make the default name of something include another item in my model?

Working with Data Node.js Frameworks
1 
const shipSchema = new mongoose.Schema({
  shipName: {
    type: String,
    required: [true, 'A ship name is required.'],
    maxlength: [60, 'That ship name is too long, please try again.'],
    unique: [true, 'Ship name already exists.'],
  },
  shipPhoto: {
    type: String,
    default: 'default.jpg',
  },
});

In the example code above, I would like for the default shipPhoto name to be the shipName string noted above, appended with “.jpg”. Is there a way for me to do this? I’m just not sure what the syntax would look like. So, for example, if shipName is “DisneyWish”, I would like for the default shipPhoto name to be “DisneyWish.jpg”. Is that possible?