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0 pointsWorldMaker3y ago0 comments

You've answered one of the easiest ways to do it: just use the same language. Node (and Deno/Bun) is a good way to maximize code sharing and single points of truth.

But I definitely understand not everyone wants to write all of their backend in JS (or even TS). (Node ORMs sometimes don't have the polish of their cousins in other languages, for instance.)

There are great opportunities here for language mixing, however, in writing that complex algorithm in the same language for both frontend and backend but the rest of the codebases may not be in the same language.

1. V8/JavaScriptCore/SpiderMonkey are all very easy to rehost as "scripting languages" inside many languages people prefer to use on the backend. It's often easy to find wrappers to call JS scripts and marshal back out their results inside the backend language of your choice these days. You pay for transitions to/from JS to your primary backend language, of course, so it takes careful management to make sure these "business rules in JS scripts" aren't in any hotpaths, but a backend may have the cycles for that anyway.

2. WASM is offering more opportunities to bring some of your preferred backend language to the frontend. You probably don't want to write your whole frontend in WASM still today, as WASM still doesn't have the same DOM access, but using WASM for single point of truth business rules has gotten quite viable. You still pay for the startup costs and marshalling costs between JS and WASM, but in many cases that's all still less than network call. (I'm still skeptical of tools like Blazor for .NET, especially those building full frontends with it, but I definitely appreciate that reach of "write once" business logic for both client and server.)

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wizofaus3y ago

You're assuming a web client. The example I had in mind was a mobile client, where we actually used a cross compiler to generate java byte code from swift to allow code sharing between iOS/Android clients, but that wasn't usable for the backends (which were C# mostly). Which is why I went with a server-precomputed lookup table in the cases the number of possible inputs made that feasible. If not, reg-exes for validation (with tooling to enable sharing between codebases) are a decent alternative in many cases. But I was curious what other options HN readers might have tried.

WorldMakerOP3y ago

Option 1 applies to mobile frontends, too. In Swift you can always call JavaScriptCore to run a script. Android can use system-wide V8 or even bundle a smaller interpreter for JS.

(In fact, JS is the only "universal" scripting language in mobile due to Apple's fun restrictions that JavaScriptCore is the only JIT engine allowed on iOS. It really is the strongest option today for language to write things in if they absolutely need to be shared across all possible operating environments.)

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