.tip

Jan 9, 2026 · one of the small things

Object.groupBy replaces the reduce you keep writing

Grouping an array by a key has been a five-line reduce for a decade. It is one line now.

const byYear = Object.groupBy(posts, (p) => new Date(p.createdAt).getFullYear());
// { 2025: [...], 2026: [...] }

Map.groupBy does the same with a Map, which keeps non-string keys and insertion order. Both are in Node 21 plus and every current browser.

javascript

~/tips/today — 2026-09-04

~cat tips/today

Session cookies: HttpOnly, Secure, SameSite=Lax

securityhttp

Three attributes, each closing a class of attack. HttpOnly keeps scripts from reading it. Secure keeps it off plain HTTP. SameSite=Lax stops it being sent on cross-site POSTs, which is most CSRF.

Set-Cookie: session=...; HttpOnly; Secure; SameSite=Lax; Path=/; Max-Age=1209600

Strict breaks arriving from an external link while logged in. Lax is the default worth keeping.

↵ open y yesterday l ls /tips

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