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Can't access cookies on client side | NodeJS and JS

Server-side code:
res.cookie('test', 'value', { expire: 400000 + Date.now(), httpOnly: false });
res.writeHead(302, {
'Location': 'localhost:4000/test',
});
res.end();
Client-side code:
When I have console.log(document.cookie); Then I can see the cookie in the console in dev tools
When I try to get one cookie console.log(document.cookie.test); or console.log(document.cookie['test']);
Then I get undefined

This is expected behavior. You are doing correct on server side.
On other side in browser cookie is saved as string separated by semi column. Each cookie contains key value pair separated by =.
In your case cookie will be like in following format:
"test=value"
If you add cookie "test2" and value "value2" you will have following format:
"test=value; test2=value2"
If you want to get value based cookie name you have to implement function which will parse string and extract value manually.
Please refer to following answer for more details.
Here is getCookie function implementation from W3Schools (this is only example, it is not tested or implemented by me):
function getCookie(cname) {
var name = cname + "=";
var decodedCookie = decodeURIComponent(document.cookie);
var ca = decodedCookie.split(';');
for(var i = 0; i <ca.length; i++) {
var c = ca[i];
while (c.charAt(0) == ' ') {
c = c.substring(1);
}
if (c.indexOf(name) == 0) {
return c.substring(name.length, c.length);
}
}
return "";
}

HTML cookie don't create

I'm having problem of creating a cookie, I have this code:
window.onload = function() {
var value = readCookie('username');
if(value == null){
alert("null");
document.cookie = "username=Bob; expires=Thu, 18 Dec 2016 12:00:00 UTC";
}
else
alert(value);
}
function readCookie(name) {
var nameEQ = name + "=";
var ca = document.cookie.split(';');
for(var i=0;i < ca.length;i++) {
var c = ca[i];
while (c.charAt(0)==' ') c = c.substring(1,c.length);
if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
}
return null;
}
When the page load I check if the cookie exists, if it doesn't, I pop up an alert saying that is null, then I create the cookie, but every time I load the page it always says its null. Now the problem is in the creation of the cookie or in the readCookie function. I can't find why this doesn't work.
UPDATE
So in google Chrome it won't work, but in internet explorer works perfectly, someone knows why? I would like to work in all browsers.

When I create an HTML page using that code and run it in a normal test environment, the problem you describe does not occur. It alerts null on the first load and Bob on the second load.
If, however, I tell the browser to load the page from file:///Users/david/tmp/jgfklgjkl/index.html instead of my test server at http://localhost:7007/, then it always alerts null.
Cookies are associated with a hostname, and you have to load the page over HTTP in order to use them.
You are presumably loading them from a local file, and that is where the problem lies, not with your code.

Try this function for reading cookie. I've been using it for quite too long and it's working fine so far
function getCookieValue(cookie_name) {
var cookie, cookies = document.cookie.split(';');
for (var i = cookies.length - 1; i >= 0; --i) {
cookie = cookies[i].split('=');
if (cookie[0].trim() === cookie_name)
return cookie[1];
}
return "";
}
Also if you are interested you could use this function for adding cookies for 10 years.
function addCookie(name, value) {
var expire = new Date();
expire.setFullYear(expire.getFullYear() + 10);
d.cookie = name + "=" + value + "; expires=" + expire.toGMTString() + "; path=/";
}

Client-side JS session library

I'm looking for a client-side JS library to store session variables.
I'd like a library that supports alternative storage medium, e.g. cookies when available with fallback on other techniques.
For instance, I found this one (but the last update is in 2009):
http://code.google.com/p/sessionstorage/
I'm not interested in security (apart a bit of data isolation among applications), as I'm not going to store sensitive data.
To give an example of use case, I want to display a message "Chrome user? Download the app" for chrome users, and I'd like to maintain a status in session to avoid displaying the message again to the same user. I don't want server-side sessions as I have caching enabled, so I must be able to serve the exact same page to different users.

You can use localStorage if available, and if it's not, then using cookies (or whatever you feel to):
var appToken = createToken();
try {
if (localStorage.getItem) {
localStorage.downloadAppAlert = appToken;
} else {
setCookie('downloadAppAlert', appToken, 10); // name, a string value, num. of days
}
} catch(e) {
console.log(e);
}
Then you can use some function to set your cookies - i.e. this one i just found in w3schools:
function setCookie(c_name,value,exdays)
{
var exdate=new Date();
exdate.setDate(exdate.getDate() + exdays);
var c_value=escape(value) + ((exdays==null) ? "" : "; expires="+exdate.toUTCString());
document.cookie=c_name + "=" + c_value;
}
To retrieve a cookie value by it's name - downloadAppAlert in the example - you can use the one on the w3schools link or something like this:
function readCookie(name) {
var nameEQ = name + '=';
var ca = document.cookie.split(';');
for(var i=0;i < ca.length;i++) {
var c = ca[i];
while (c.charAt(0)==' ') c = c.substring(1,c.length);
if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
}
return null;
}
Also, to retrieve a previously setted item on the localStorage you simply:
var appToken = localStorage.getItem('downloadAppAlert');
EDIT: Sorry, with the hurries i forgot to mention what createToken() does. It is supposed to be a random alphanumeric generator function. You can find plenty on SO, like:
Random alpha-numeric string in JavaScript?
Generate random string/characters in JavaScript
Generating (pseudo)random alpha-numeric strings

Use node-client-sessions (https://github.com/mozilla/node-client-sessions) by mozilla.

Session only cookies with Javascript

I was wondering if it's possible to create session only cookies with Javascript. When the browser is closed the cookies should be removed.
I can't use anything on the server as the website is HTML only ... so no server side script is used.
I read something about this here:
http://blog.lysender.com/2011/08/setting-session-only-cookie-via-javascript/
but i can't find any more information about this ... so i was wondering if this method is reliable.

Yes, that is correct.
Not putting an expires part in will create a session cookie, whether it is created in JavaScript or on the server.
See https://stackoverflow.com/a/532660/1901857
For the use case in the question (no server side code), sessionStorage is a simpler solution. But sessionStorage is client only, so would not work if you need to access the stored value on the server (e.g. user logins etc.)

A simpler solution would be to use sessionStorage, in this case:
var myVariable = "Hello World";
sessionStorage['myvariable'] = myVariable;
var readValue = sessionStorage['myvariable'];
console.log(readValue);
However, keep in mind that sessionStorage saves everything as a string, so when working with arrays / objects, you can use JSON to store them:
var myVariable = {a:[1,2,3,4], b:"some text"};
sessionStorage['myvariable'] = JSON.stringify(myVariable);
var readValue = JSON.parse(sessionStorage['myvariable']);
A page session lasts for as long as the browser is open and survives over page reloads and restores. Opening a page in a new tab or window will cause a new session to be initiated.
So, when you close the page / tab, the data is lost.

For creating session only cookie with java script, you can use the following. This works for me.
document.cookie = "cookiename=value; expires=0; path=/";
then get cookie value as following
//get cookie
var cookiename = getCookie("cookiename");
if (cookiename == "value") {
//write your script
}
//function getCookie
function getCookie(cname) {
var name = cname + "=";
var ca = document.cookie.split(';');
for (var i = 0; i < ca.length; i++) {
var c = ca[i];
while (c.charAt(0) == ' ') c = c.substring(1);
if (c.indexOf(name) != -1) return c.substring(name.length, c.length);
}
return "";
}
Okay to support IE we can leave "expires" completely and can use this
document.cookie = "mtracker=somevalue; path=/";

Use the below code for a setup session cookie, it will work until browser close. (make sure not close tab)
function setCookie(cname, cvalue, exdays) {
var d = new Date();
d.setTime(d.getTime() + (exdays*24*60*60*1000));
var expires = "expires="+ d.toUTCString();
document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}
function getCookie(cname) {
var name = cname + "=";
var decodedCookie = decodeURIComponent(document.cookie);
var ca = decodedCookie.split(';');
for(var i = 0; i <ca.length; i++) {
var c = ca[i];
while (c.charAt(0) == ' ') {
c = c.substring(1);
}
if (c.indexOf(name) == 0) {
return c.substring(name.length, c.length);
}
}
return false;
}
if(getCookie("KoiMilGaya")) {
//alert('found');
// Cookie found. Display any text like repeat user. // reload, other page visit, close tab and open again..
} else {
//alert('nothing');
// Display popup or anthing here. it shows on first visit only.
// this will load again when user closer browser and open again.
setCookie('KoiMilGaya','1');
}

Cookie always return null in IE

I'm debugging a script, that basically reads a cookie and returns some stuff. It works fine in all browsers, except for IE. After some testing, I discover that it never enters the for loop.
function readCookie(name) {
var nameEQ = name + "=";
var ca = document.cookie.split(';');
for(var i=0;i < ca.length;i++) {
var c = ca[i];
while (c.charAt(0)==' ') c = c.substring(1,c.length);
if (c.indexOf(nameEQ) == 0) {
return c.substring(nameEQ.length,c.length);
}
}
return null;
}
After some more testing, I realize the variable ca, which store the cookie, never even gets defined. Looking at it, I don't see why it should, as there is no reference to the cookiename. So in my logic, it shouldn't even work, yet it works perfectly in everything but IE.
var ca = document.cookie.split(';');
1: Why does this even work in Fx, Webkit and Opera?
2: How can I make it work in IE as well?
I tried defining it as below, but that didn't seem to work:
document.cookie = name;

It appears there are no cookies set in IE. Try using
alert('d.cookie:\t'+document.cookie+'\n\n'+'d.cookie.length:\t'+document.cookie.length);
to check if there are any cookies.
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If there are none, try setting one using
document.cookie='mycookie=foo; path=/';
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