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What is your folder-structure preference for a large-scale Node.js project?

0: Starting from Rails

This is the reference point. All the other options are based off this.

|-- app
|   |-- controllers
|   |   |-- admin
|   |   |   |-- postsController.js
|   |   |   `-- usersController.js
|   |   |-- postsController.js
|   |   |-- sessionsController.js
|   |   `-- usersController.js
|   |-- models
|   |   |-- post.js
|   |   `-- user.js
|   |-- views
|   |   |-- admin
|   |   |   `-- posts
|   |   |       |-- edit.jade
|   |   |       |-- index.jade
|   |   |       |-- new.jade
|   |   |-- layouts
|   |   |   `-- application.jade
|   |   `-- posts
|   |       |-- index.jade
|   |       `-- show.jade
|   `-- helpers
|       |-- admin
|       |   |-- postsHelper.js
|       |   `-- tagsHelper.js
|       `-- postsHelper.js
`-- config
|    |-- application.js
|    |-- locale
|        `-- en.js
|    |-- routes.js
`-- lib
`-- spec
|    |-- helper.js
|    |-- models
|    |   |-- postSpec.js
|    |   |-- userSpec.js
|    `-- acceptance
|        |-- loginSpec.js
|        |-- signupSpec.js
|        `-- postsSpec.js
`-- vendor
|    |-- javascripts
|    |   |-- jquery.js
|    |   |-- underscore.js
|    `-- stylesheets
|        `-- prettyPhoto.css

1: Rails-like, with nested /app folders for client, mobile, etc.

|-- app
|   |-- controllers
|   |-- models
|   |-- views
|   `-- browser
|       |-- controllers
|       |-- models
|       |-- views
|   `-- mobile
|       |-- controllers
|       |-- models
|       |-- views
`-- config
`-- lib
`-- spec
`-- vendor

Pros:

• lends itself great to progressive enhancement so-to-speak. You start with just /app, and if your app starts growing, you add sub directories.
• doesn't pollute the top-level directories, which have a pretty uniform convention across apps. However, people do add /themes to the top level, which is just about the same as adding /client to the top-level.

Cons:

• Now you have /app/models and /app/browser, etc., which isn't a totally clear naming convention -- /app/models is for a subset of code for the server, while /app/browser is a totally different app. It's different than a namespace like /app/models/admin though, which makes sense.

My vote: no

2: A /app/client folder, similar to Rails' /app/assets

|-- app
|   |-- controllers
|   |-- models
|   |-- views
|   `-- client
|       `-- browser
|           |-- controllers
|           |-- models
|           |-- views
|       `-- mobile
|           |-- controllers
|           |-- models
|           |-- views
`-- config
`-- lib
`-- spec
`-- vendor

Pros:

• The main reason you need these extra folders is for the different clients for the app. So putting them in /app/client conceptually makes a lot of sense. It's easy to reason about.
• Similar to Rails, which has /app/assets/javascripts instead of /app/client. You don't want to start naming the folder /app/assets because, conceptually, everything is JavaScript, and calling one chunk of JavaScript "assets" and the rest "app" is conceptually jarring.

Cons:

• You have deeply nested folders for core code, which can be annoying. /app/client/browser/controllers/postsController.js is 4 folders down. But with TextMate and CMD+T, it shouldn't be an issue.

You could also have this structure if you only had 1 client (or just a default client):

|-- app
|   |-- controllers
|   |-- models
|   |-- views
|   `-- client
|       |-- controllers
|       |-- models
|       `-- views

That's pretty clear, and it lends itself to agile development really well.

My vote: ✔

3: More top-level folders

|-- app
|   |-- controllers
|   |-- models
|   |-- views
|-- browser
|   |-- controllers
|   |-- models
|   |-- views
|-- mobile
|   |-- controllers
|   |-- models
|   |-- views
`-- config
`-- lib
`-- spec
`-- vendor

Pros:

• Minimum folder nesting
• model/view/controller folders are all at the same level

Cons:

• Having multiple top-level folders, all of which are mvc code, is not conceptually clear. They should be part of one directory (taking us back to #2). Having every folder at the top level be a completely conceptually distinct part of the app (database vs. app vs. config vs. tests) is a clarifying convention.

My vote: second choice, but no

4: Namespaces inside /app

|-- app
|   `-- client
|       |-- controllers
|       |-- models
|       |-- views
|   `-- mobile
|       |-- controllers
|       |-- models
|       |-- views
|   `-- server
|       |-- controllers
|       |-- models
|       |-- views
`-- config
`-- lib
`-- spec
`-- vendor

Pros:

• Clear, normalized separation of concerns. Everything fits into the same folder structure, instead of having the "default" stuff in /app, and then also nesting components in there.

Cons:

• For the simple case, you have to create a nested folder.
  • Counterargument: But, you're setup to easily add other clients for the app
• By not having the default code go in the top level /app, it's not as clear that server code can be used on the client (e.g. using /app/server/models/user.js on the client. it makes sense if it's in /app/models/user.js however.).

My vote: no

5: Top-level /client and /server directories

This breaks convention, but it's an option. Rename /app to /server

|-- client
|   |-- controllers
|   |-- models
|   |-- views
|-- server
|   |-- controllers
|   |-- models
|   |-- views
`-- config
`-- lib
`-- spec
`-- vendor

Pros:

• Clear: there is a client and server app.

Cons:

• If you had multiple client apps (browser, mobile, ipad, etc.), you'd end up doing things like #2 or #3.

My vote: no

Which do you prefer?

I prefer folder structure #2.