LowFile-scopeJavaScript / TypeScript Plug & play

Optimize chained array operations

Prefer a single pass when possible (e.g., reduce) over multiple filter/map chains on the same array.

Why this matters

Cuts allocations and improves throughput on hot paths.

Side-by-side examples engineers can pattern-match during review.

Avoid

const out = xs.filter(p).map(f).filter(q);

Prefer

const out = xs.reduce((acc,x)=>{ if(!p(x)) return acc; const y=f(x); if(q(y)) acc.push(y); return acc; },[]);

Bad

arr.filter().map().filter()

Good

arr.reduce((acc,x)=>{/* combine */},[])

From the same buckets as this rule.

Critical
Avoid Blocking Calls to Async Methods
Blocking async methods with `.Result` or `.Wait()` can cause deadlocks and prevent efficient asynchronous execution. Use `await` instead for proper async behavior.
concurrency-safetyperformance-efficiency
Critical
Fingerprint assets and cache immutably
All static JS/CSS/font/image files MUST use content-hashed filenames (e.g., app.9c1a7b.js) and be served with "Cache-Control: public, max-age=31536000, immutable". HTML and other non-fingerprinted documents MUST be served with "Cache-Control: no-cache" (or equivalent) to enable conditional revalidation.
web-static-assetscaching-strategy+2
Critical
No live network or DB in unit tests—use fakes/mocks
Unit tests must stub or fake external HTTP/DB calls; allow real I/O only in integration/e2e tests tagged accordingly.
testing-qualityperformance-efficiency+1