How to sort collections in Meteor

I thought it's clear how to sort collections in Meteor, but it isn't for beginners. MongoDB uses $orderby operator for sorting and Meteor uses sort operator. It might not be clear how to use sort operator in Meteor from its docs.

Let's say we have a collection named Messages:

Messages = new Mongo.Collection('messages');

The schema of the collection looks like this:

{
  _id: String,
  text: String,
  username: String,
  timestamp: Number
}

Then we want to publish messages with limit and sort operator/option:

Meteor.publish('messages', function(limit) {
  return Messages.find({}, {
    limit: limit || 5,
    sort: { timestamp: -1 }
  });
});

sort: { timestamp: -1 } option means that we sort messages by timestamp in descendant order. If we wanted to sort messages by timestamp in ascendant order, we would use sort: { timestamp: 1 }.

Call subscribe on the client:

Meteor.subscribe('messages', 10); //subscribe 10 messages 

Write a helper that returns sorted messages. It's not enough to call Messages.find(); because it would not sort messages by timestamp:

Template.messages.helpers({
  messages: function () {
    return Messages.find({}, {
      sort: { timestamp: -1 }
    });
  }
});

Now just show messages in a template:

<template name="messages">
  {{#each messages}}
    <p>{{username}}: {{text}}</p>
  {{/each}}
</template>

That's all. I have created a chat application which you can clone and play with it: https://github.com/Elfoslav/meteor-chat-tutorial

Learn more about using MongoDB in Meteor in this video: https://www.youtube.com/watch?v=TOBex9L5Acs&index=8&list=PLoy-bs-bDKThDssbowaKGqaD_rneci8rd

 

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