[Reference][Snippet][MongooseJS]: Listen and bind on "open" event aka "on connect"

mongoosejs.on.connect.js

// This snippet is useful for debugging connection parameters in the connect_string, for checking if your remote mongodb server is up, etc.  

var mongoose = require("mongoose");
mongoose.connect(connect_string);
mongoose.connection.on("open", function(){
  console.log("connection established");
})