ExpressJS - Cookies


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Cookies are simple, small files/data that are sent to client with a server request and stored on the client side. Every time the user loads the website back, this cookie is sent with the request. This helps us keep track of the user’s actions.

The following are the numerous uses of the HTTP Cookies −

  • Session management
  • Personalization(Recommendation systems)
  • User tracking

To use cookies with Express, we need the cookie-parser middleware. To install it, use the following code −

npm install --save cookie-parser

Now to use cookies with Express, we will require the cookie-parser. cookie-parser is a middleware which parses cookies attached to the client request object. To use it, we will require it in our index.js file; this can be used the same way as we use other middleware. Here, we will use the following code.

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

cookie-parser parses Cookie header and populates req.cookies with an object keyed by the cookie names. To set a new cookie, let us define a new route in your Express app like −

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

app.get('/', function(req, res){
   res.cookie('name', 'express').send('cookie set'); //Sets name = express
});

app.listen(3000);

To check if your cookie is set or not, just go to your browser, fire up the console, and enter −

console.log(document.cookie);

You will get the output like (you may have more cookies set maybe due to extensions in your browser) −

"name = express"

The browser also sends back cookies every time it queries the server. To view cookies from your server, on the server console in a route, add the following code to that route.

console.log('Cookies: ', req.cookies);

Next time you send a request to this route, you will receive the following output.

Cookies: { name: 'express' }

Adding Cookies with Expiration Time

You can add cookies that expire. To add a cookie that expires, just pass an object with property 'expire' set to the time when you want it to expire. For example,

//Expires after 360000 ms from the time it is set.
res.cookie(name, 'value', {expire: 360000 + Date.now()}); 

Another way to set expiration time is using 'maxAge' property. Using this property, we can provide relative time instead of absolute time. Following is an example of this method.

//This cookie also expires after 360000 ms from the time it is set.
res.cookie(name, 'value', {maxAge: 360000});

Deleting Existing Cookies

To delete a cookie, use the clearCookie function. For example, if you need to clear a cookie named foo, use the following code.

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

app.get('/clear_cookie_foo', function(req, res){
   res.clearCookie('foo');
   res.send('cookie foo cleared');
});

app.listen(3000);

In the next chapter, we will see how to use cookies to manage sessions.



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