# Flash Messages
Flash messaging in Express can be confusing to the newcomer. I know because I am a newcomer. The confusion tends to arise from the distinction between the concept of flash messaging, a temporary message from the server available to templates, and the various implementations of flash messaging, which include `express-flash` and other modules. This Gist provides a minimal example of 2 approaches to flash messaging, the `express-flash` module and custom middleware, using 3 common templating engines. 

The `express-flash` module exposes getter and setter methods for a flash message of the form, `{ flash: { type: 'type', message: 'message' }}` and depends on the `express-session` module. The method `req.flash(type, message)` sets the value of a new flash message and adds it to an array of messages of the same type. The method `req.flash(type)` gets the value of all flash messages matching of the same type and returns either a string value for the message if there is only 1 of that type, or an array of string values for messages matching that type. The flash messages have a lifetime of one request and are deleted afterward. 

The custom middleware is lifted with modifications from Ethan Brown's excellent book, Web Development with Node & Express, and depends on the `express-session` module. In it, `res.locals.sessionFlash` acts as a the getter and `req.session.sessionFlash` acts as the setter for messages with a lifetime of one request. As in the `express-flash` module, these flashes take the form, `{ type: 'type', message: 'message' }`, but only do so to follow established convention. They could as easily take the form, `{ class: 'class', intro: 'intro', text: 'text' }` and be exposed via `res.locals.myFlashMessages` and `req.session.myFlashMessages`.

There are a couple of important distinctions between the 2 approaches illustrated above. 

First, the custom middleware option exposes all of the properties of the flash object, not just the message. So `sessionFlash.type` and `sessionFlash.message` are both available to the templates above just by including the `sessionFlash` value, whereas the `expressFlash` message `type` would have to have been explicitly specified in `app.js` and passed as a separate value, ie `expressFlashType`,  to the template. 

Second, the custom middleware does not include a mechanism for adding multiple messages of the same type to an array. As it is written, `res.locals.sessionFlash` and `req.session.sessionFlash` are single occupancy variables.

Of note, `res.locals.flash` and `req.session.flash` can be used in the custom middleware above, but I chose different targets to avoid collision with the `express-flash` messages.

Both approaches offer simple mechanisms for passing temporary messages to the browser. Which one of the many options you choose depends on your needs. I hope this has been helpful.