JavaScript

24 April 2026 15:01

👀 Windows 95 as an Electron App

A full Windows 95 experience as an app on macOS, Linux, and Windows, built upon the v86 JavaScript + WASM emulator. v5.0 is a big release as you can mount a folder from your machine into it as a Z: drive, mount ISOs as CD-ROMs, there’s a shared clipboard, and Internet access has been improved. I’m so trying to get Microsoft Encarta’s Mindmaze running on this…

Felix Rieseberg

JavaScript

23 April 2026 15:09

🤔 Boneyard: Auto-Generated Skeleton Screens for Your UI

Snapshots your real UI and captures a flat list of skeleton ‘bones’ which are positioned, sized rectangles that mirror the page exactly. Supports React, Preact, React Native, Vue, Svelte, and Angular.

0xGF

JavaScript

22 April 2026 15:03

🌕 Installing Every Firefox Extension

One person’s entertaining and heroic tale of wielding JavaScript to explore the Firefox extension ecosystem. And what oddities there are within! I enjoyed this a lot, it’s like Alice in Wonderland for developers. More spelunking like this please.

Jack Cab

JavaScript

21 April 2026 17:44

😮 Under the Hood of MDN's New Frontend

The hugely useful MDN has rebuilt its frontend stack from the ground up, ditching React for web components and a homegrown server component system. A great read on building a modern, content-heavy site without shipping unnecessary JavaScript on every page.

Leo McArdle (MDN)

JavaScript

21 April 2026 08:31

CHALLENGE

const str = "  Hello, World!  ";

const result = str
  .trim()
  .split(", ")
  .map((word, i) => {
    return i === 0
      ? word.toUpperCase()
      : word.replace(/!$/, "").split("").reverse().join("") + "?";
  })
  .join(" | ");

const [first, ...rest] = result.split(" | ");
const final = `${first} | ${rest.join(" & ")}`;

console.log(final);

JavaScript

11 April 2026 19:26

✌️ V8 Exploitation: From Libc Pwn to Browser Bugs

For the past few years I've been doing pwn challenges - starting from basic stack overflows, progressing through libc heap exploitation, writing a CheatEngine clone in Rust, and prototyping an eBPF-based record-replay tool that required bypassing vDSO. I felt fairly comfortable with systems programming and userspace exploitation.

But challenges like QEMU escape or browser exploitation always seemed like a different league. Something I wasn't "ready for yet." That feeling created an artificial barrier - I kept telling myself I needed more preparation before even attempting them.

....

D4RK7ET (Varik Matevosyan)

JavaScript

10 April 2026 15:07

👀 Fuse.js 7.3: Lightweight Fuzzy-Search

Want a search feature tolerant to ambiguous input without a dedicated backend? v7.3 adds per-term fuzzy matching and a static method for single string matching, while v7.4 beta adds worker-based distributed search for tackling huge datasets. A demo shows off the basics.

Kiro Risk

JavaScript

09 April 2026 15:07

In CSS is DOOMed, Niels Leenheer shows off how he implemented a version of 1993's Doom using purely CSS rendering (with the game logic in JavaScript). Play it for yourself or check out the code.

JavaScript

07 April 2026 21:06

✌️ JSIR: A High-Level IR for JavaScript from Google

Google has open sourced a new tool (JSIR) and proposed an industry-standard IR (Intermediate Representation – if an AST tells you what the code looks like, an IR tells you what it does) for JavaScript. Already used at Google for analysis and code transformation, the underlying idea could form a foundation for a new generation of tooling.

Zhixun Tan (Google)

JavaScript

04 April 2026 09:40

🔥 Tragic mistake... Anthropic leaks Claude’s source code

Fireship

JavaScript

03 April 2026 08:35

CHALLENGE

const delay = (ms, val) => new Promise(res => setTimeout(res, ms, val));

const p1 = delay(300, "alpha");
const p2 = Promise.reject("network error");
const p3 = delay(100, "gamma");
const p4 = Promise.reject("timeout");

Promise.allSettled([p1, p2, p3, p4]).then(results => {
  const summary = results.map(r =>
    r.status === "fulfilled"
      ? `ok:${r.value}`
      : `fail:${r.reason}`
  );
  console.log(summary.join(" | "));
});

JavaScript

02 April 2026 08:33

CHALLENGE

function* range(start, end) {
  while (start < end) {
    yield start++;
  }
}

function* evens(iter) {
  for (const val of iter) {
    if (val % 2 === 0) yield val;
  }
}

function* take(n, iter) {
  let count = 0;
  for (const val of iter) {
    if (count++ >= n) return;
    yield val;
  }
}

function* pipeline() {
  yield* take(3, evens(range(1, 20)));
  yield* take(2, range(10, 15));
}

const result = [...pipeline()];
console.log(result);

JavaScript

31 March 2026 08:34

CHALLENGE

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

const language = "javascript";
const year = 2015;
const feature = "templates";

const output = highlight`Language: ${language}, introduced in ${year}, feature: ${feature}!`;
console.log(output);

JavaScript

29 March 2026 08:34

CHALLENGE

const obj = {
  name: "Quantum",
  regular: function () {
    return this.name;
  },
  arrow: () => {
    return this?.name;
  },
  nested: function () {
    const inner = () => this.name;
    return inner();
  },
};

console.log(obj.regular());
console.log(obj.arrow());
console.log(obj.nested());

JavaScript

27 March 2026 07:30

CHALLENGE

const operations = {
  add: (a, b) => a + b,
  subtract: (a, b) => a - b,
  multiply: (a, b) => a * b,
  divide: (a, b) => b !== 0 ? a / b : null,
};

const pipeline = (...fns) => (value) => fns.reduce((acc, fn) => fn(acc), value);

const double  = (x) => operations.multiply(x, 2);
const addTen  = (x) => operations.add(x, 10);
const halve   = (x) => operations.divide(x, 2);
const subtractThree = (x) => operations.subtract(x, 3);

const transform = pipeline(double, addTen, halve, subtractThree);

console.log(transform(5));

JavaScript

24 April 2026 08:32

CHALLENGE

class Animal {
  #sound;

  constructor(name, sound) {
    this.name = name;
    this.#sound = sound;
  }

  speak() {
    return `${this.name} says ${this.#sound}`;
  }

  static create(name, sound) {
    return new this(name, sound);
  }
}

class Dog extends Animal {
  #tricks = [];

  constructor(name) {
    super(name, "woof");
  }

  learn(trick) {
    this.#tricks.push(trick);
    return this;
  }

  perform() {
    return `${this.name} performs: ${this.#tricks.join(", ")}`;
  }
}

const rex = Dog.create("Rex", "bark");
rex.learn("sit").learn("shake").learn("roll over");

console.log(rex.speak());
console.log(rex.perform());
console.log(rex instanceof Animal);
console.log(rex instanceof Dog);

JavaScript

23 April 2026 08:30

CHALLENGE

const values = [0.1 + 0.2, NaN, Infinity, -0, 42.6789];

const results = values.map((v, i) => {
  if (i === 0) return Number.isInteger(v) + " " + v.toFixed(1);
  if (i === 1) return Number.isFinite(v) + " " + Number.isNaN(v);
  if (i === 2) return Number.isFinite(v) + " " + isFinite(v);
  if (i === 3) return Object.is(v, -0) + " " + (v === 0);
  if (i === 4) return v.toPrecision(4) + " " + Math.trunc(v);
});

results.forEach(r => console.log(r));

JavaScript

22 April 2026 08:34

CHALLENGE

const prefix = 'user';
const id = 42;
const role = 'admin';

const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1);

const profile = {
  [`${prefix}_${id}`]: 'Marcus',
  [Symbol.iterator]: null,
  [`get${capitalize(role)}`]: () => 'full-access',
  [`${prefix}Count`]: 3,
};

const dynamicKey = `${prefix}_${id}`;

console.log(
  profile[dynamicKey],
  profile[`get${capitalize(role)}`](),
  profile[`${prefix}Count`] * id,
  Object.keys(profile).length
);

JavaScript

21 April 2026 08:31

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

20 April 2026 08:33

CHALLENGE

function checkTDZ() {
  console.log(typeof undeclaredVar);

  try {
    console.log(typeof letVar);
  } catch (e) {
    console.log(`Caught: ${e.constructor.name}`);
  }

  let letVar = "initialized";

  const result = (() => {
    let x = 10;
    return function () {
      let x = x + 5;
      return x;
    };
  })();

  try {
    console.log(result());
  } catch (e) {
    console.log(`Caught: ${e.constructor.name}`);
  }
}

checkTDZ();

JavaScript

11 April 2026 08:32

CHALLENGE

const config = {
  host: "localhost",
  port: 3000,
  db: {
    name: "mydb",
    retries: 5
  }
};

Object.freeze(config);

config.port = 9999;
config.newProp = "injected";
config.db.retries = 99;
delete config.host;

console.log(
  config.port,
  config.newProp,
  config.db.retries,
  config.host
);

JavaScript

10 April 2026 08:33

CHALLENGE

const name = "Carlos";
const age = 28;
const score = 95;

const player = {
  name,
  age,
  score,
  greet() {
    return `${this.name} (${this.age}) scored ${this.score}`;
  },
  get rank() {
    return this.score >= 90 ? "Gold" : "Silver";
  }
};

const { name: playerName, rank, greet } = player;

console.log(`${playerName} | ${rank} | ${greet.call(player)}`);

JavaScript

09 April 2026 08:32

CHALLENGE

function createUser(
  name,
  role = "viewer",
  permissions = [role],
  metadata = { createdBy: name, level: permissions.length }
) {
  return { name, role, permissions, metadata };
}

const user1 = createUser("Carlos");
const user2 = createUser("Diana", "admin", ["read", "write", "delete"]);
const user3 = createUser("Eve", "editor", undefined, { createdBy: "system", level: 99 });

console.log(user1.role, user1.permissions, user1.metadata.level);
console.log(user2.metadata.createdBy, user2.permissions.length);
console.log(user3.permissions[0], user3.metadata.level);

JavaScript

07 April 2026 08:30

CHALLENGE

function Vehicle(make, model, year) {
  this.make = make;
  this.model = model;
  this.year = year;
  this.speed = 0;
}

Vehicle.prototype.accelerate = function (amount) {
  this.speed += amount;
  return this;
};

Vehicle.prototype.describe = function () {
  return `${this.year} ${this.make} ${this.model} going ${this.speed}km/h`;
};

function ElectricVehicle(make, model, year, range) {
  Vehicle.call(this, make, model, year);
  this.range = range;
}

ElectricVehicle.prototype = Object.create(Vehicle.prototype);
ElectricVehicle.prototype.constructor = ElectricVehicle;

ElectricVehicle.prototype.describe = function () {
  return Vehicle.prototype.describe.call(this) + ` | Range: ${this.range}km`;
};

const car = new ElectricVehicle("Tesla", "Model 3", 2023, 500);
car.accelerate(60).accelerate(40);

console.log(car.describe());
console.log(car instanceof ElectricVehicle);
console.log(car instanceof Vehicle);
console.log(car.constructor === ElectricVehicle);

JavaScript

04 April 2026 08:33

CHALLENGE

const str = "  Hello, World!  ";

const result = str
  .trim()
  .split(", ")
  .map((word, i) => {
    if (i % 2 === 0) return word.toUpperCase();
    return word.toLowerCase().replace("!", "@");
  })
  .reverse()
  .join(" | ");

console.log(result);

JavaScript

02 April 2026 09:01

🤔 axios Package Compromised; Malicious Versions Added a Trojan Dependency

Axios is an HTTP library that gets 100M+ downloads a week, largely due to its legacy popularity. An attacker took advantage of that to roll out a version with a malicious dependency including a remote access trojan (though Axios' codebase itself was fine). This is big, as even if you don’t use Axios, your dependencies might. Here's how to see if you're affected.

Ashish Kurmi

JavaScript

01 April 2026 08:33

CHALLENGE

const handler = {
  get(target, prop, receiver) {
    if (prop in target) {
      return Reflect.get(target, prop, receiver) * 2;
    }
    return `Missing: ${prop}`;
  },
  set(target, prop, value) {
    if (typeof value !== "number") {
      throw new TypeError("Only numbers allowed");
    }
    return Reflect.set(target, prop, Math.abs(value));
  },
};

const store = new Proxy({ gold: 10, silver: 5 }, handler);

store.bronze = -42;

console.log(store.gold);
console.log(store.bronze);
console.log(store.platinum);

JavaScript

30 March 2026 08:30

CHALLENGE

const curry = (fn) => {
  const arity = fn.length;
  return function curried(...args) {
    if (args.length >= arity) {
      return fn(...args);
    }
    return (...moreArgs) => curried(...args, ...moreArgs);
  };
};

const volume = (l, w, h) => l * w * h;
const curriedVolume = curry(volume);

const withLength5 = curriedVolume(5);
const withLength5Width3 = withLength5(3);

console.log(typeof withLength5);
console.log(typeof withLength5Width3);
console.log(withLength5Width3(4));
console.log(curriedVolume(2)(6)(7));

JavaScript

28 March 2026 07:31

CHALLENGE

"use strict";

function createCounter() {
  let count = 0;

  return {
    increment() { count++; },
    getCount() { return count; },
    reset: function() { count = 0; }
  };
}

const counter = createCounter();
counter.increment();
counter.increment();
counter.increment();

const { getCount, reset } = counter;

try {
  reset();
  console.log("After reset:", counter.getCount());
} catch (e) {
  console.log("Error:", e.message);
}

console.log("Direct call:", counter.getCount());

JavaScript

26 March 2026 14:04

👀 The Three Pillars of JavaScript Bloat

Three reasons your node_modules is huge: needless ES3-era compat packages, micro-libraries with a single consumer, and ponyfills for APIs that shipped years ago! James, known for the e18e ecosystem performance project, offers some ways to calm the chaos.

James Garbutt