cool-socket.js

var coolSocket = conenct.behavior("cool-socket", function(base){
  
  return {
    init: function(){
      this.socket = something();
      this.socket.wasOffAndNowIsOn(function(){
        // get last date from localStorage
        var lastDate = READ_FROM_LOCALSTORAGE;
        this.socket.get(extend({},set, {since: lastDate})).then(function(newData){
            newData.data.forEach(this.createInstance)
        })
      })
    },
    getListData: function(set){
      // 
      return this.cacheConnection.getListData(set).then(function(cachedData){
        var lastDate = READ_FROM_LOCALSTORAGE;
        this.socket.ready.then(()=>{
          this.socket.get(extend({},set, {since: lastDate})).then(function(newData){
            return {data: cacheData.data.concat(newData.data)}
          })
        })
      })
    }
  }
});


connect([
  require("can-connect/constructor/"),
  require("can-connect/constructor/store/"),
  ... // all other behaviors here
  coolSocket
],{
  algebra: ...,
  Map: Todo,
  ...
})


Todo.getList({});