How can I set cookie in node js using express framework?

Question

The order in which you use middleware in Express matters: middleware declared earlier will get called first, and if it can handle a request, any middleware declared later will not get called.

If express.static is handling the request, you need to move your middleware up:

// need cookieParser middleware before we can do anything with cookies
app.use(express.cookieParser());

// set a cookie
app.use(function (req, res, next) {
  // check if client sent cookie
  var cookie = req.cookies.cookieName;
  if (cookie === undefined) {
    // no: set a new cookie
    var randomNumber=Math.random().toString();
    randomNumber=randomNumber.substring(2,randomNumber.length);
    res.cookie('cookieName',randomNumber, { maxAge: 900000, httpOnly: true });
    console.log('cookie created successfully');
  } else {
    // yes, cookie was already present 
    console.log('cookie exists', cookie);
  } 
  next(); // <-- important!
});

// let static middleware do its job
app.use(express.static(__dirname + '/public'));

Also, middleware needs to either end a request (by sending back a response), or pass the request to the next middleware. In this case, I've done the latter by calling next() when the cookie has been set.

Update

As of now the cookie parser is a seperate npm package, so instead of using

app.use(express.cookieParser());

you need to install it separately using npm i cookie-parser and then use it as:

const cookieParser = require('cookie-parser');
app.use(cookieParser());

Set Cookie?

res.cookie('cookieName', 'cookieValue')

Read Cookie?

req.cookies

Demo

const express('express')
    , cookieParser = require('cookie-parser'); // in order to read cookie sent from client

app.get('/', (req,res)=>{

    // read cookies
    console.log(req.cookies) 

    let options = {
        maxAge: 1000 * 60 * 15, // would expire after 15 minutes
        httpOnly: true, // The cookie only accessible by the web server
        signed: true // Indicates if the cookie should be signed
    }

    // Set cookie
    res.cookie('cookieName', 'cookieValue', options) // options is optional
    res.send('')

})

Not exactly answering your question, but I came across your question, while looking for an answer to an issue that I had. Maybe it will help somebody else.

My issue was that cookies were set in server response, but were not saved by the browser.

The server response came back with cookies set:

Set-Cookie:my_cookie=HelloWorld; Path=/; Expires=Wed, 15 Mar 2017 15:59:59 GMT 

This is how I solved it.

I used fetch in the client-side code. If you do not specify credentials: 'include' in the fetch options, cookies are neither sent to server nor saved by the browser, even though the server response sets cookies.

Example:

var headers = new Headers();
headers.append('Content-Type', 'application/json');
headers.append('Accept', 'application/json');

return fetch('/your/server_endpoint', {
    method: 'POST',
    mode: 'same-origin',
    redirect: 'follow',
    credentials: 'include', // Don't forget to specify this if you need cookies
    headers: headers,
    body: JSON.stringify({
        first_name: 'John',
        last_name: 'Doe'
    })
})

Set a cookie:

res.cookie('cookie', 'monster')

https://expressjs.com/en/4x/api.html#res.cookie

Read a cookie:
(using cookie-parser middleware)

req.cookies['cookie']

https://expressjs.com/en/4x/api.html#req.cookies

Setting cookie in the express is easy

1. first install cookie-parser

npm install cookie-parser

2. using middleware

const cookieParser = require('cookie-parser');
app.use(cookieParser());

3. Set cookie know more

res.cookie('cookieName', '1', { expires: new Date(Date.now() + 900000), httpOnly: true })

4. Accessing that cookie know more

console.dir(req.cookies.cookieName)

Done!