Extra properties on Mongoose schema field? - node.js

Question

Is it possible to add extra / custom attributes to the field in a Mongoose schema? For example, note the name: attribute on the following fields:
var schema = mongoose.Schema({
_id : { type: String, default: $.uuid.init },
n : { type: String, trim: true, name: 'name' },
ac : { type: Date, required: true, name: 'created' },
au : { type: Date, name: 'updated' },
ad : { type: Date, name: 'deleted' },
am : { type: String, ref: 'Member', required: true, name: 'member' }
});
We expect to have a large number of docs in our system and would like to conserve as much space as possible. In this example, we have abbreviated the name of the fields (n vs name, etc.). We would like to use the additional name field to hydrate a JSON object after a fetch.

Answer 1

You could create an instance method (which I called toMappedObject, but you're free to name it however you like) that could perform the conversion by checking the schema for each field to see if it has a name property:
schema.methods.toMappedObject = function() {
let obj = this.toObject();
Object.keys(obj).forEach(fieldName => {
let field = schema.tree[fieldName];
if (field.name) {
obj[field.name] = obj[fieldName];
delete obj[fieldName];
}
});
return obj;
}
// Example usage:
let doc = new Model({...});
let obj = doc.toMappedObject();
Alternatively, you can configure your schema to automatically transform the output generated by toJSON, although it's much more implicit so easy to overlook in case issues pop up (I haven't tested this very well):
schema.set('toJSON', {
transform : function(doc, obj) {
Object.keys(obj).forEach(fieldName => {
let field = doc.schema.tree[fieldName];
if (field.name) {
obj[field.name] = obj[fieldName];
delete obj[fieldName];
}
});
return obj;
}
});
// Example usage:
let doc = new Model({...});
console.log('%j', doc); // will call `doc.toJSON()` implicitly