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Flash Fiction.js

NPM version

Flash Fiction.js is an object for storing keys and values and later serializing unused/unread ones. It's primarily useful for storing informational and error messages in web apps for page rendering or redirects. It comes with middleware for Connect.js and Express.js that stores unused messages in signed cookies for the next request. It's similar in spirit to Rails's ActionDispatch::Flash.

The middleware works with Express v4 and assumes you've set up cookie-parser with a secret. Another cookie parser library will work, too, if it has an equivalent API (res.signedCookies).


npm install flash-fiction

Flash Fiction.js follows semantic versioning, so feel free to depend on its major version with something like >= 1.0.0 < 2 (a.k.a ^1.0.0).


var Express = require("express")
var app = Express()

After the Flash middleware has run, you'll have flash functions available on the request and response objects for getting and setting messages respectively.

In your HTTP handler, call res.flash to set a message (you can pass it any JSON-compatible value):"/models", function(req, res) {
  // ... Something that saves the model.
  res.flash("info", "Created successfully.")

Then once your client's browser follows the redirect, you have req.flash to read the value back out:

app.get("/models/:id", function(req, res) {
  if (req.flash("info")) console.log(req.flash("info"))

The getter function is also available as a local variable in templates.
For example, a Jade/Pug template would look like the following:

if flash("error")
  h1 Uh-oh!
  p= flash("error")

Accessing Immediately Without Redirect

Sometimes you don't need to do a redirect, but would still like to use the flash object for passing messages to the view. Set and get flash messages as before with res.flash("info", msg) and req.flash("info"). You can access set messages immediately on req.flash. Flash Fiction.js is even also smart enough to then not serialize that used key for the next request.

Serializing for JavaScript

If you'd like to pass the flash messages from Node's side to client side JavaScript, you can call flash without any arguments in your template to get all the messages back.

script window.flash = #{JSON.stringify(flash()).replace(/<\//g, "<\\/")}

Remember to escape </ lest you create a security vulnerability due to in-band signaling of one <script> tag's end and the other's beginning.

Using without Connect/Express

If you'd like to use the Flash object yourself without the middleware, require it:

var Flash = require("flash-fiction")
var flash = new Flash({info: "OK"})
flash.set("notice", "OMG")
flash.get("info") // => "OK"
flash.get() // => {info: "OK", notice: "OMG"}


Flash Fiction.js is released under a Lesser GNU Affero General Public License, which in summary means:

  • You can use this program for no cost.
  • You can use this program for both personal and commercial reasons.
  • You do not have to share your own program's code which uses this program.
  • You have to share modifications (e.g. bug-fixes) you've made to this program.

For more convoluted language, see the LICENSE file.


Andri Möll typed this and the code.
Monday Calendar supported the engineering work.

If you find Flash Fiction.js needs improving, please don't hesitate to type to me now at or create an issue online.


Flash messages middleware for Express/Connect with support for redirects and immediate use. Useful for informational or errors messages. Like Rails's Flash.







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