socket.io-当需要socket.io时在严格模式下使用const

Question

我遵循关于socket.io的入门教程，但是当我提到要包含socket.io本身时，在控制台中运行服务器时出现错误。

我想念什么？

var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);

app.get('/', function(req, res){
    res.sendFile(__dirname + '/index.html');
});

io.on('connection', function(socket){
    console.log('a user connected');
});

http.listen(3000, function(){
    console.log('listening on *:3000');
});

错误：

/usr/share/nginx/html/server/node_modules/socket.io/lib/index.js:177
  const keysIterator = this.parentNsps.keys();
  ^^^^^
SyntaxError: Use of const in strict mode.
    at Module._compile (module.js:439:25)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)
    at require (module.js:380:17)
    at Object.<anonymous> (/usr/share/nginx/html/server/index.js:3:10)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)