1) 40% less code. Size does matter, simple scales better.

2) Cleaner code design: Functional first, OO as needed, no more Class-For-Everything induced contortionism.

3) Cleaner module public API: intent driven function with related types, class often as a module implementation details (when needed).

4) Better typing: TypeScript modern structural typing model reduce typing friction while maximizing expressiveness.

5) More maintained library community. Suprisingly we found npm libraries (the good ones) better maintained than their counter part with simpler/cleaner API (google sdk, opencv, ..)

6) Much fewer files: No more 1-1 between module and file. Same module file can export all needed for a service, functions, const, and types, and can even re-export external module structure.

7) Same advanced "enterprise/CRUD/..." feature set, "AOP" like with decorators for RBAC and perf instrumentation, full DAO and Service layer fully reimplemented (with much less Class).

8) Maximum code reuse between server, micro-services (also in TS), and client (also in TS).

9) Ironically, orchestrating advanced concurrency in nodejs can be better achieved than in Java standard programming, as nio/async is ubiquitous, async/await/promise is simply powerful.

10) Did some domain-specific benchmarking, and while Java is about 2x faster on a single concurrency mode, node.js was 2x once turning concurrency to 100.

Can probably make Java scale with quite a bit of work, but even if Java vs NodeJS perf is a wash, the value above are too important to ignore.

After 20 years of Java, we are starting all our new #BigApp enterprise/cloud projects with nodejs/typescript now. The only caveat now is to fight clich├ęs.