Ask HN: How to get the ease of SPA on the back-end?

Does anyone have experience with a Handlebars like equivalent for the back-end? It would be great to get the ease of which you can produce components/reusable modules on the back-end without necessarily being tied to a specific back-end (e.g. Rails templates, C# templates).

In Ember there's Fastboot which would give you both (a single way to write all of your templates, but are served from your back-end), but it's not ready for prime-time quite yet. Another nice thing about Ember in particular is that your templates are standardized with handlebars, so theoretically you could switch from Ember and not have to do that much work on the template-end.

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I'm a fan of keeping your back-end and front-end decoupled, but it would be nice to also have the advantages that back-end served templates give you, as well. It might be a pipe-dream, but I folks here might have some experience.