Didin J wrote a nice tutorial on how to build a chat application with Socket.io, MongoDB, Express, Vue.js 2 and Node.js (MEVN).

vue.js app

MEVN Tutorial: The comprehensive tutorial on MongoDB, Express, Vue.js 2, Node.js (MEVN) and SocketIO Chat Application. Previously we have a tutorial on build chat application using MEAN Stack, now we build this chat application using MEVN (MongoDB, Express.js, Vue.js 2, Node.js) Stack. The different just now we use Vue.js 2 and Axios, we keep using MongoDB, Node.js, Express, and Socket.io.