JavaScript

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CHALLENGE function tag(strings, ...values) { return strings.raw.join('|') + '=' + values.reduce((sum, v) => sum + v, 0); } const x = 5; const y = 10; console.log(tag`Sum\n${x}and${y}end`);

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CHALLENGE let arr = []; for (let i = 0; i < 3; i++) { if (i === 1) { let i = 10; arr.push(i); continue; } arr.push(i); } console.log(arr.join('-'));

CHALLENGE const order = []; const log = (s) => order.push(s); log('start'); Promise.resolve().then(() => { log('p1'); return Promise.resolve(); }).then(() => log('p1-2')); async function foo() { log('foo-start'); await null; log('foo-end'); } foo(); Promise.resolve().then(() => log('p2')); log('end'); setTimeout(() => console.log(order.join(' ')), 0);

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CHALLENGE class Config { constructor(options = {}) { this.retries = options.retries ?? 3; this.timeout = options.timeout ?? 1000; } } const cfg1 = new Config({ retries: 0, timeout: null }); const cfg2 = new Config({ retries: undefined, timeout: false }); cfg1.retries ??= 99; cfg2.timeout ??= 99; console.log(cfg1.retries, cfg1.timeout, cfg2.retries, cfg2.timeout);

CHALLENGE const a = [] + {}; const b = {} + []; const c = 1 + '1' - 1; const d = '5' + 3 - 2; const e = true + true; console.log(a, b, c, d, e);

👀 Next.js 16.3 Released The newly expanded Next.js team (now including Dan Abramov and 𝕏 Pete Hunt!) has dropped the latest version of the popular React framework, complete with faster builds, optional TypeScript 7 type checking, faster SSR, Instant Navigations, AI improvements, and more. The Next.js Team

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CHALLENGE function memoize(fn) { const cache = new Map(); return (...args) => { const key = JSON.stringify(args); if (cache.has(key)) return cache.get(key); const result = fn(...args); cache.set(key, result); return result; }; } let calls = 0; const add = memoize((a, b) => { calls++; return a + b; }); const r1 = add(1, 2); const r2 = add(2, 1); const r3 = add(1, 2); console.log(r1, r2, r3, calls);

CHALLENGE const Loggable = { log() { return `[${this.constructor.name}] ${this.toString()}`; } }; class Base { toString() { return 'Base instance'; } } Object.setPrototypeOf(Base.prototype, Loggable); class Derived extends Base { toString() { return 'Derived instance'; } } const b = new Base(); const d = new Derived(); console.log(b.log(), d.log(), Object.getPrototypeOf(Derived.prototype) === Base.prototype);

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CHALLENGE const str = "2024-01-15"; const result = str.replace(/(\d+)-(\d+)-(\d+)/, "$3/$2/$1"); const s2 = "abc".padStart(6, "12"); const s3 = [..."hello"].reverse().join(""); console.log(result, s2, s3);

↗️ TanStack Charts: A New Chart Grammar Option In the past few weeks, TanStack has been rapidly iterating on a new, framework-neutral way to declaratively specify a large number of chart-related visualizations in JavaScript. Output renders to SVG or canvas and can be styled as you wish. Here's a comparison against other established options. TanStack

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🤟 Node.js 26.7.0 (Current) Released Landing just two days after 26.6, coverage reports can now include files your tests didn't touch with --test-coverage-include-all, FFI and SQLite pick up crash fixes, and Perfetto tracing support lands, though you'll need a custom build to use it. Antoine du Hamel