JavaScript

09 August 2026 08:33

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);

JavaScript

07 August 2026 08:34

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);

JavaScript

05 August 2026 08:33

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`);

JavaScript

03 August 2026 08:32

CHALLENGE

function tag(strings, ...values) {
  // strings.raw preserves literal escape sequences
  const rawParts = strings.raw;
  let result = rawParts.join('|');
  result += '::' + values.join(',');
  return result;
}

const x = 5;
const output = tag`Line1\nLine2${x}End`;
console.log(output);

JavaScript

02 August 2026 08:30

CHALLENGE

function* inner() {
  yield 1;
  yield 2;
  return 10;
}

function* outer() {
  const result = yield* inner();
  yield result;
  yield 3;
}

const gen = outer();
const a = gen.next().value;
const b = gen.next().value;
const c = gen.next().value;
const d = gen.next().value;
console.log(a, b, c, d);

JavaScript

01 August 2026 08:31

CHALLENGE

class Base {
  static count = 0;
  static #secret;
  static {
    Base.#secret = 10;
    Base.count += 1;
  }
  static getSecret() {
    return Base.#secret;
  }
}

class Derived extends Base {
  static {
    Base.count += 100;
  }
}

console.log(Base.count, Derived.count, Base.getSecret());

JavaScript

30 July 2026 08:31

CHALLENGE

const source = {
  _val: 1,
  get val() { return this._val; }
};
const copy1 = Object.assign({}, source);
source._val = 100;
const copy2 = { ...source };
copy1._val = 999;
console.log(copy1.val, copy2.val, source.val, copy1._val);

JavaScript

28 July 2026 08:31

CHALLENGE

const primArr = [1, 2, 3];
const copyArr = [...primArr];
copyArr[0] = 99;

const objArr = [{ x: 1 }, { x: 2 }];
const copyObjArr = [...objArr];
copyObjArr[0].x = 99;

console.log(primArr[0], copyArr[0], objArr[0].x, copyObjArr[0].x);

JavaScript

27 July 2026 08:35

CHALLENGE

class Timer {
  constructor() { this.seconds = 0; }
  start() {
    this.tick = () => { this.seconds++; return this.seconds; };
    return this.tick;
  }
}

const t = new Timer();
const tick = t.start();
const obj = { seconds: 100, tick };
console.log(tick(), obj.tick(), t.seconds);

JavaScript

25 July 2026 14:09

😮 How a Fake Interview's Coding Challenge Steals Credentials

A dissection of a North Korean campaign that hides malware inside SVG images in a fake job interview's JavaScript 'coding challenge'. The targeting of job-seeking devs is on the increase, as Roman Imankulov recently discovered first-hand.

Daniel Stepanic (Elastic)

JavaScript

23 July 2026 13:04

🤩 Flint: Chart Specs that Compile to Vega-Lite, ECharts, or Chart.js

A Microsoft project that compiles a simple, declarative JSON-based spec of a data visualization into a form that Vega-Lite, ECharts or Chart.js can render. It's pitched at agentic use, but is a simple intermediate format humans could benefit from too.

Microsoft Research

JavaScript

21 July 2026 08:34

CHALLENGE

function* pipeline(...fns) {
  let value = yield;
  for (const fn of fns) {
    value = yield fn(value);
  }
  return value;
}

const double  = x => x * 2;
const addTen  = x => x + 10;
const square  = x => x * x;

const gen = pipeline(double, addTen, square);

gen.next();           // prime the generator
const r1 = gen.next(3);
const r2 = gen.next(r1.value);
const r3 = gen.next(r2.value);

console.log(r1.value, r2.value, r3.value);

JavaScript

19 July 2026 08:32

CHALLENGE

const p1 = new Promise((resolve) => {
  console.log("A");
  resolve("B");
});

const p2 = p1.then((val) => {
  console.log(val);
  return "C";
});

p2.then((val) => {
  console.log(val);
});

console.log("D");

JavaScript

17 July 2026 16:14

☔️ AWS billing issues

JavaScript

16 July 2026 08:33

CHALLENGE

function createUser(
  name,
  role = "viewer",
  permissions = { read: true, write: false },
  level = permissions.write ? 2 : 1
) {
  return { name, role, permissions, level };
}

const user1 = createUser("Carlos");
const user2 = createUser("Diana", "editor", { read: true, write: true });
const user3 = createUser("Eve", "admin", undefined, 5);

console.log(user1.role, user1.level);
console.log(user2.role, user2.level);
console.log(user3.role, user3.level);

JavaScript

08 August 2026 08:30

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('-'));

JavaScript

06 August 2026 08:30

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);

JavaScript

04 August 2026 08:32

CHALLENGE

const config = { retries: 0, timeout: null, name: '' };
const a = config.retries || 5;
const b = config.timeout ?? 10;
const c = config.name || 'default';
const d = config.missing?.value ?? 'fallback';
let calls = 0;
const sideEffect = () => { calls++; return true; };
const e = config.retries && sideEffect();
console.log(a, b, c, d, e, calls);

JavaScript

02 August 2026 15:02

🥶 scriptc: Vercel's New TypeScript-to-Native Compiler

A new entry into the growing field of JS/TS native ahead-of-time compilers that makes the promise that "what compiles behaves byte-for-byte like Node." Static by default, but you can opt in to a --dynamic mode which embeds a JavaScript engine for runtime dynamism. GitHub repo.

Vercel Labs

JavaScript

01 August 2026 17:00

⛽️ The Secure Way to Release an npm Package in 2026

A practical guide to publishing npm packages more safely in 2026, written by someone who's released several popular packages (like postcss and nanoid). As well as showing how to use things like staged publishing and trusted publishing, he explains why and the security benefits of doing so.

Andrey Sitnik

JavaScript

31 July 2026 08:30

CHALLENGE

function Animal(name) {
  this.name = name;
}
Animal.prototype.speak = function () {
  return `${this.name} makes a sound`;
};

function Dog(name) {
  Animal.call(this, name);
}
Dog.prototype = Object.create(Animal.prototype);
Dog.prototype.constructor = Dog;
Dog.prototype.speak = function () {
  return `${Animal.prototype.speak.call(this)} (bark)`;
};

const d = new Dog('Rex');
console.log(
  d.speak(),
  d instanceof Animal,
  d.constructor === Dog,
  Object.getPrototypeOf(d) === Dog.prototype
);

export {};

JavaScript

29 July 2026 08:33

CHALLENGE

const arr = [1, [2, 3], [4, [5, 6]], 7];
const a = arr.flat();
const b = arr.flat(2);
const c = arr.flatMap(x => Array.isArray(x) ? x : [x, x]);
const d = [1, 2, 3].flatMap(x => [[x]]);
console.log(JSON.stringify([a, b, c, d]));

JavaScript

27 July 2026 14:02

🙂 Follow a Single HTTP Request Through Its ~200ms Life

From the creator of NodeBook, a thorough guide to Node's internals, comes a scroll-driven visualization following every step a single HTTP POST request takes from the user's click to Node's event loop and on to a database behind it.

Ishtmeet Singh

JavaScript

26 July 2026 14:02

😲 LiteParse 2: Fast, Light PDF Document Parsing

A PDF parser built in Rust with bindings for Node (plus WASM, Rust, and Python) — it worked great in my testing. It includes OCR, handles layouts/is spatially aware, and is fast (a complex 140-page PDF took ~10 seconds). Here's how to get started from Node.

LlamaIndex

JavaScript

24 July 2026 14:04

Famously, the only thing Java gave JavaScript was the first four letters of its name. That goes unmentioned in 😉 this new documentary about Java (74 minutes), but I enjoyed learning Java's story anyway. It's from the same folks as the fantastic Vite, Angular, and Node.js documentaries.

JavaScript

22 July 2026 12:01

😃 Framework Benchmarks: Compare Frontend Frameworks

An experienced developer built and benchmarked the same app across numerous frameworks (e.g. Angular, Solid, React, Alpine.js…). Here are the results, covering bundle size, build time, UX metrics, and more.

Alicia Sykes

JavaScript

20 July 2026 08:31

CHALLENGE

function highlight(strings, ...values) {
  return strings.reduce((result, str, i) => {
    const value = values[i - 1];
    const transformed =
      typeof value === "number"
        ? `[${value * 2}]`
        : `(${String(value).toUpperCase()})`;
    return result + transformed + str;
  });
}

const product = "widget";
const qty = 4;
const price = 12.5;

const output = highlight`Order: ${product} x${qty} @ $${price}`;
console.log(output);

JavaScript

18 July 2026 08:33

CHALLENGE

const tag = (strings, ...values) => {
  return strings.reduce((result, str, i) => {
    const value = values[i - 1];
    const transformed =
      typeof value === "number" ? value * 2 : value?.toUpperCase();
    return result + transformed + str;
  });
};

const name = "carlos";
const score = 42;
const bonus = null;

const output = tag`Player: ${name}, Score: ${score}, Bonus: ${bonus}`;
console.log(output);

JavaScript

17 July 2026 08:33

CHALLENGE

const user = {
  profile: {
    name: "Marcus",
    address: {
      city: "Berlin",
      zip: "10115"
    }
  },
  getSubscription: () => ({
    plan: "pro",
    features: ["analytics", "exports"]
  })
};

const city       = user?.profile?.address?.city;
const country    = user?.profile?.address?.country?.toUpperCase();
const firstFeature = user?.getSubscription?.()?.features?.[0];
const adminRole  = user?.roles?.[0]?.name ?? "guest";

console.log(city, country, firstFeature, adminRole);

JavaScript

15 July 2026 08:34

CHALLENGE

const flags = {
  READ:    0b0001,
  WRITE:   0b0010,
  EXECUTE: 0b0100,
  DELETE:  0b1000,
};

const userPermissions = flags.READ | flags.WRITE | flags.EXECUTE;
const adminPermissions = userPermissions | flags.DELETE;

const canDelete = (adminPermissions & flags.DELETE) !== 0;
const readOnly  = userPermissions & ~flags.WRITE;

const toggled = userPermissions ^ flags.EXECUTE;
const shifted = (flags.DELETE << 2) | (flags.READ >> 0);

console.log(canDelete, readOnly, toggled, shifted);