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fromEntries ​

Problem ​

You have an array of [key, value] pairs and need to reconstruct a typed record from them — the typed counterpart to Object.fromEntries.

Solution ​

Use fromEntries(input) to convert an iterable of key-value pairs back into an object.

ts
import { entries, fromEntries, mapValues } from '@vielzeug/arsenal';

const config = { host: 'localhost', port: 3000 };

// Round-trip via entries/fromEntries
const doubled = fromEntries(entries(config).map(([k, v]) => [k, typeof v === 'number' ? v * 2 : v]));
// { host: 'localhost', port: 6000 }

Pitfalls ​

  • Duplicate keys: the last pair wins.