Do something when a document is added to a MongoDB collection in Meteor

Meteor-collection-observe.es6.js

Meteor.startup(function() {

  let leadsLoaded = false;
  let leadsCursor = Leads.find();

  Meteor.subscribe('leads', function() {
    leadsLoaded = true;
  });

  leadsCursor.observe({

    added: function(doc) {

      if(leadsLoaded) {

        const title = 'You Have a New Lead!';
        const body = `Name: ${doc.first_name} ${doc.last_name}`;

        renderDesktopNotification(title, body);

      }
    }
  });

});