What is the best way to require node modules var or const?

When we are requiring node modules to suck as express, bodyParser we will use var keyword to create a variable and assign the module. Can't we use the const to declare such modules?

var express = require('express');
var app = express();

or defining above as be

const express = require('express');
const app = express();

What is the best way? and why is that?

via Dhanuka Perera