An example of auto reload on deploy in an Elixir Phoenix app

socket.js

import {Socket} from "phoenix"

let socket = new Socket("/socket", { params: {} })
socket.connect()

let channel = socket.channel("updates", {})
channel.join()

// Reload the app if it's out of date when it joins the websocket
let revision = null
channel.on("welcome", welcome => {
  if(!revision) { revision = welcome.revision }
  if(revision != welcome.revision) { window.location.reload() }
})

updates_channel.ex

defmodule MyApp.UpdatesChannel do
  use Phoenix.Channel

  def join(_channel, _message, socket) do
    send self, :after_join
    {:ok, socket}
  end

  def handle_info(:after_join, socket) do
    # HEROKU_SLUG_COMMIT is available through https://devcenter.heroku.com/articles/dyno-metadata
    push socket, "welcome", %{ revision: System.get_env("HEROKU_SLUG_COMMIT") }
    {:noreply, socket}
  end
end