On front end I use React.js. I also know Angular.js and some Vue.js that And on back end I prefer Node.js and using this framework I can handle the tasks of any complicity. If needed I can involve other tools like of course Express.js, as well as socket.io, mean.js or Meteor. If you are not sure about your back end technology – I strongly recommend to look at Node.js. It gives you speed of work, you probably understand what advantages gives JavaScript back end. And also if you need to save time or just do not want to make the project too complicated – you can take ready tool from Node package manager.