const options = { discriminatorKey: 'kind' };
const Event = mongoose.model('Event, new Schema({
 name: { type: String }
}, options);

const ClickEvent = Event.discriminator('ClickEvent', new Schema({
 url: { type: String }
}, options);

// on another file
const ClickEvent = mongoose.model('ClickEvent');
const clickEvent = new ClickEvent({
 name: 'sir',
 url: 'http://somewhere.com/hello'
});
console.log(clickEvent); // { name: 'sir', url: 'http://somewhere.com/hello', kind: 'ClickEvent' }
// look carefully kind is set to ClickEvent

const ClickEvent = Event.discriminator('ClickEvent', new Schema({
     url: { type: String }
    }, { ...options, discriminatorValue: 'click' });