Nodejs: Path must be a string. Received null

Question

I was trying to implement the following code and got the TypeError error when I ran it.

app.js

var app = module.exports = require('express').createServer();
var io = require('socket.io').listen(app);
var path = require('path');

app.listen(3000);

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

io.sockets.on('connection', function(socket){
    socket.emit('welcome', {text: 'Welcome!!!'});
});

Error Output:

TypeError: Path must be a string. Received null
    at assertPath (path.js:8:11)
    at posix.join (path.js:479:5)
    at exports.send (/Users/rluo/Desktop/learn/learnNode/socket.io_epxress/node_modules/express/node_modules/connect/lib/middleware/static.js:129:20)
    at ServerResponse.res.sendfile (/Users/rluo/Desktop/learn/learnNode/socket.io_epxress/node_modules/express/lib/response.js:186:3)
    at /Users/rluo/Desktop/learn/learnNode/socket.io_epxress/app.js:8:6
    at callbacks (/Users/rluo/Desktop/learn/learnNode/socket.io_epxress/node_modules/express/lib/router/index.js:272:11)
    at param (/Users/rluo/Desktop/learn/learnNode/socket.io_epxress/node_modules/express/lib/router/index.js:246:11)
    at pass (/Users/rluo/Desktop/learn/learnNode/socket.io_epxress/node_modules/express/lib/router/index.js:253:5)
    at Router._dispatch (/Users/rluo/Desktop/learn/learnNode/socket.io_epxress/node_modules/express/lib/router/index.js:280:5)
    at Object.Router.middleware [as handle] (/Users/rluo/Desktop/learn/learnNode/socket.io_epxress/node_modules/express/lib/router/index.js:45:10)

package.json:

{
    "name":"socketio_express-example",
    "version":"0.0.1",
    "private":true,
    "dependencies":{
        "socket.io":"0.8.7",
        "express":"2.5.4"
    }
}

Thanks in advance.

Answer 1

• The error is pretty clear, you need to specify an absolute (instead of relative) path

Examples:

// assuming index.html is in the same directory as this script

res.sendFile(__dirname + '/index.html');

• You do not need path at all Global Objects

__dirname Added in: v0.1.27

The name of the directory that the currently executing script resides in.for more detail https://nodejs.org/docs/latest/api/globals.html

• check this thread TypeError: Path must be a string

• Creating socket

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

  var http = require('http').Server(app);

  Express initializes app to be a function handler that you can supply to an HTTP server (as seen in line 2). socket.io

__dirname vs path

Answer 2

Before you use res.sendFile() you need to set static files directory like below.

var express = require('express');
var app = express();
app.use(express.static(path.join(__dirname+'your index or static files location'));
app.get('/',function(req,res){
   res.sendFile(__dirname+'index.html');
});

Answer 3

Please use the 'path' module that you have required. Try this:

app.get('/',function(req,res){
    res.sendfile(path.join(__dirname, '/index.html'));
});