server.js

/*
 * Using Yjs on nodejs is not very different
 * from using it in the browser. It is *just another client*!
 *
 * start this server with
 * `` node server.js room-name ``
 *
 * It will join the specified room and act as a master client. Therefore, you can set the syncMethod to master-slave
 */

if(process.argv[2] == null){
 throw new Error("You must specify a room-name! E.g. node server.js my-room");
}

var Y = require('yjs');
Y.XMPP = require('y-xmpp');

var connector = new Y.XMPP({
  host: "yatta.ninja", // You _must_ specify the host, when using it with nodejs (this is our testing server)
  defaultRoomComponent: "@conference.yatta.ninja" // You _must_ specify this, if you want to use the room on _your_ server
}).join(process.argv[2], {role: "master"});

connector.debug = true

var y = new Y(connector);
var feed = y.val("feed",[],"mutable").val("feed");

/*
 * The server has the function to not allow a feed size greater that 15.
 * When a greater number is reached, it will automatically delete the
 * oldest posts.
*/

var feed_size = 15;

feed.observe(function(){
  // whenever something changed, check if the feed size exceeds 15
  var length = feed.val().length;
  if(length > feed_size){
    feed.delete(feed_size,length-feed_size)
  }
})
console.log("listening!")