AngularJS best practice - Templates vs Javascript

I've never wondered about that issue myself. One possible idea would be to reuse the pattern known as assets versioning, where upon new release, you rename all your assets.

For instance, instead of login.html you'd use login-xyz.html as a name of a template. xyz could be a random value, or a checksum of the file. Checksum might be a slightly better option because if the new release is small (i.e. you fixed just some small bug in one file), if user loads any page but the fixed one, he/she will not be bothered with a reload - all other files will have the same checksums, they'll work with no interruptions.

This way, when an outdated Anguar app tries to fetch a template, it'd get a HTTP 404 error. As an addition to that, you could write a simple $http interceptor, which would detect a 404 response, and reload page automatically (or offer user an option of doing so).

There are modules which are capable of renaming assets, such as gulp-rev - but I never heard of using that for Angular templates. You might implement something like that on your own, though.

Of course you might want to keep both the new and old versions of files to allow users to work without interrupting them with a refresh. Depends on what your requirements are. I assume you're trying to avoid that, though.

Sample 404 interceptor (CoffeScript, as I have it handy now):

m.factory 'notFoundInterceptor', ($q) -> return { responseError: (response) -> if response?.status == 404 # Reload, or warn user return $q.defer() # Not a 404, so handle it elsewhere $q.reject response } m.config ($httpProvider) -> $httpProvider.interceptors.push 'notFoundInterceptor' 

I've read about this issue long time ago, and one option is to do versioning on changed pages and application.js file.

For example on your version 1 of your application you can on your html file use something like:

<script src="js/angular_app_v1.js"></script> 

Inside your routes also version the templateURL

templateUrl: 'templates/view_product_v1.html' 

So when you roll out a new version you won't be overwriting templates and users already working will have the old version until they reload the browser but won't have version inconsistences.

Versioning of the assets using the file names would become unmaintainable for even a medium sided app.

Although it is a heavy weight approach for web assets you could look into content negotiation. This is where the call for a resource, generally a REST api returns the version of the resource, Content-Type: application/vnd.contentful.delivery.v1+json.. On the client you can check that the version matches what it expects. So if the client only knows how to load v1.1 and the resource responses with v1.2 the UI would know it cannot process that and should reload the page.

Another possibility is to load all templates up front in the UI. There are build processes in Grunt you can run such as https://github.com/ericclemmons/grunt-angular-templates that will combine all of your templates into a single file for delivery and then load them into $templateCache so no requests ever get to the server.

If you have some sort of server-side language you can build a filter in (.NET, Rails, Java or whatever), and pass along a version number with your template requests. If the version requested by the client is older than what's deployed, you'd send an error to the client. Your client would watch for that error ($http interceptor) and force a page-refresh to pull down the newer javascript code. (Maybe show an alert to the user first so they know what's going on).

You can preload all your templates into a $templateCache and serve them as one templates.js file. There is a gulp task for this https://www.npmjs.com/package/gulp-angular-templatecache. Then your application will load all templates in a single request together with application scripts on start up, thus they will be in sync. Read http://www.johnpapa.net/angular-and-gulp/ for more info.

It always makes sense to have a version number and use it when syncing resources. It's not only a good practice for the use case you described, but also for other situation, such as rolling back to a specific version or having two versions live and usable (for example in order to let some users preview the next version)