When or why would I use a marionette.behavior?

Question

I've been reading the marionette docs and I can't seem to figure out when I would use a marionette.behavior.

Because, from what I understand, this is the same as extending another view that already has the same resulting actions.

So what is it that I missed that would explain the use of marionette.behavior ?

Presuppose

Answer 1

Its not quite same.

Behavior its like mix-in. It should have a very specified responsibility for e.g : tooltip, alert or like this.

Of course you can do it with extending view that has same functionality, but if you need to implement few different logics like you need popup, alert and label functionality - you will have to build chain with extend.

As you understand its harder to read, maintain and you may loose in performance. Behaviors lets you implement few logics at once:

var MyView = Marionette.ItemView.extend({
  ui: {
    "close": ".close-btn"
  },

  behaviors: {
    CloseWarn: {
      message: "you are closing all your data is now gone!"
    },
    ToolTip: {
      text: "what a nice mouse you have"
    }
  }
});

This code is much clearer and readable.

So using behaviors expect them as mix-in of very specified function. Make it as small as possible. Don't let them "know much".

Evidence

Would behavior be too small to implement something like a custom scrollbar where I add whole bunch ui elements through the behavior? – Toulon

@Xzigraz, Your view should only render (in some cases update) model data, all interactions should be placed in behavior, especially reusable interactions. Custom scrollbar is a great example of possible Behavior usage – Evidence