Simple cookie-based session middleware.
A user session can be stored in two main ways with cookies: on the server or on the client. This module stores the session data on the client within a cookie, while a module like express-session stores only a session identifier on the client within a cookie and stores the session data on the server, typically in a database.
The following points can help you choose which to use:
cookie-sessiondoes not require any database / resources on the server side, though the total session data cannot exceed the browser's max cookie size.
cookie-sessioncan simplify certain load-balanced scenarios.
cookie-sessioncan be used to store a "light" session and include an identifier to look up a database-backed secondary store to reduce database lookups.
$ npm install cookie-session
var cookieSession =var express =var app =app
Create a new cookie session middleware with the provided options. This middleware
will attach the property
req, which provides an object representing
the loaded session. This session is either a new session if no valid session was
provided in the request, or a loaded session from the request.
The middleware will automatically add a
Set-Cookie header to the response if the
req.session were altered. Note that no
Set-Cookie header will be
in the response (and thus no session created for a specific user) unless there are
contents in the session, so be sure to add something to
req.session as soon as
you have identifying information to store for the session.
Cookie session accepts these properties in the options object.
The name of the cookie to set, defaults to
The list of keys to use to sign & verify cookie values. Set cookies are always
keys, while the other keys are valid for verification, allowing
for key rotation.
A string which will be used as single key if
keys is not provided.
Other options are passed to
cookies.set() allowing you
to control security, domain, path, and signing among other settings.
The options can also contain any of the following (for the full list, see cookies module documentation:
maxAge: a number representing the milliseconds from
Dateobject indicating the cookie's expiration date (expires at the end of session by default).
path: a string indicating the path of the cookie (
domain: a string indicating the domain of the cookie (no default).
sameSite: a boolean or string indicating whether the cookie is a "same site" cookie (
falseby default). This can be set to
true(which maps to
secure: a boolean indicating whether the cookie is only to be sent over HTTPS (
falseby default for HTTP,
trueby default for HTTPS). If this is set to
trueand Node.js is not directly over a TLS connection, be sure to read how to setup Express behind proxies or the cookie may not ever set correctly.
signed: a boolean indicating whether the cookie is to be signed (
trueby default). If this is true, another cookie of the same name with the
.sigsuffix appended will also be sent, with a 27-byte url-safe base64 SHA1 value representing the hash of cookie-name=cookie-value against the first Keygrip key. This signature key is used to detect tampering the next time a cookie is received.
overwrite: a boolean indicating whether to overwrite previously set cookies of the same name (
trueby default). If this is true, all cookies set during the same request with the same name (regardless of path or domain) are filtered out of the Set-Cookie header when setting this cookie.
Represents the session for the given request.
true if the session has been changed during the request.
true if the session is new.
Determine if the session has been populated with data or is empty.
Represents the session options for the current request. These options are a shallow clone of what was provided at middleware construction and can be altered to change cookie setting behavior on a per-request basis.
To destroy a session simply set it to
req.session = null
var cookieSession =var express =var app =app // trust first proxyappappapp
var cookieSession =var express =var app =app // trust first proxyapp// This allows you to set req.session.maxAge to let certain sessions// have a different value than the default.app// ... your logic here ...
This module does not send a
Set-Cookie header if the contents of the session
have not changed. This means that to extend the expiration of a session in the
user's browser (in response to user activity, for example) some kind of
modification to the session needs be made.
var cookieSession =var express =var app =app// Update a value in the cookie so that the set-cookie will be sent.// Only changes every minute so that it's not sent with every request.app// ... your logic here ...
Because the entire session object is encoded and stored in a cookie, it is possible to exceed the maxium cookie size limits on different browsers. The RFC6265 specification recommends that a browser SHOULD allow
At least 4096 bytes per cookie (as measured by the sum of the length of the cookie's name, value, and attributes)
In practice this limit differs slightly across browsers. See a list of browser limits here. As a rule of thumb don't exceed 4093 bytes per domain.
If your session object is large enough to exceed a browser limit when encoded, in most cases the browser will refuse to store the cookie. This will cause the following requests from the browser to either a) not have any session information or b) use old session information that was small enough to not exceed the cookie limit.
If you find your session object is hitting these limits, it is best to consider if data in your session should be loaded from a database on the server instead of transmitted to/from the browser with every request. Or move to an alternative session strategy