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CHALLENGE

const teams = [
{ name: 'Warriors', players: ['Curry', 'Thompson'] },
{ name: 'Lakers', players: ['James', 'Davis'] }
];

const newTeams = JSON.parse(JSON.stringify(teams));
newTeams[0].players.push('Green');

const shallowCopy = [...teams];
shallowCopy[1].name = 'Clippers';

const freezeTest = Object.freeze({nested: {value: 42}});
freezeTest.nested.value = 100;

console.log(teams[1].name, teams[0].players.length, freezeTest.nested.value);
6🤣3
3👍3🔥3
CHALLENGE

let x = 5;

function foo() {
console.log(x);
let x = 10;
console.log(x);
}

foo();
1
💻 Deno 2.4: deno bundle is Back

Deno 2.4 reintroduces the deno bundle command for creating single-file bundles for both the server and client side, complete with support for npm and JSR dependencies and automatic tree-shaking. You can also now include arbitrary files into modules using import, and Deno’s built-in OpenTelemetry support is now stable. It’s a substantial release.

Iwańczuk and Jiang
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3👍2🔥1
CHALLENGE

const fruits = ['apple', 'banana', 'cherry'];
const newFruits = [...fruits];

newFruits.push('date');

const user = { name: 'Taylor', age: 30 };
const updatedUser = { ...user, age: 31 };

user.city = 'Seattle';

console.log(fruits.length, newFruits.length, user.city, updatedUser.city);
3
CHALLENGE

const handler = {
get(target, prop) {
if (prop in target) {
return target[prop] * 2;
} else {
return `Property ${prop} not found`;
}
},
set(target, prop, value) {
if (typeof value === 'number') {
target[prop] = Math.round(value);
return true;
}
return false;
}
};

const obj = { a: 5, b: 10 };
const proxy = new Proxy(obj, handler);

proxy.c = 7.8;
proxy.d = "hello";

console.log(obj.c, proxy.a, proxy.x);
1
🤔 How to Build Your Own Color Search Engine

A straightforward, practical look at bringing together several technologies and skills to create an AI powered color suggestion tool (which you can try here – results may vary, as seen above). The techniques covered can be used for many different practical ends.

Lúí Smyth
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CHALLENGE

const map = new WeakMap();

let obj1 = { name: 'user1' };
let obj2 = { name: 'user2' };

map.set(obj1, 'data for user1');
map.set(obj2, 'data for user2');

console.log(map.has(obj1));
obj1 = null;

// After garbage collection runs
console.log(map.has(obj1));
console.log(map.get(obj2));
👍 Milkdown: A Plugin-Driven WYSIWYG Markdown Editor Framework

A WYSIWYG Markdown editor framework based around a plugin system that enables a significant level of customization. The docs are rendered by Milkdown itself and there’s a neat ‘playground’ experience to try as well. GitHub repo.

Mirone
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2👍2🔥1
CHALLENGE

function createCounter() {
let count = 0;

function increment() {
count++;
return count;
}

function decrement() {
count--;
return count;
}

return { increment, decrement, reset: () => count = 0 };
}

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

const { increment, reset } = counter;
increment();
reset();
increment();

console.log(counter.increment());
What is the output?
Anonymous Quiz
32%
1
42%
2
13%
3
14%
undefined
🔥52👍1
😆
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CHALLENGE

function processUserData(data) {
try {
if (!data) {
throw new Error('No data provided');
}

if (!data.name) {
throw new TypeError('Name is required');
}

return { success: true, user: data.name };
} catch (err) {
if (err instanceof TypeError) {
return { success: false, reason: 'validation-failed' };
}
return { success: false, reason: 'unknown-error' };
}
}

console.log(processUserData({}));
2
CHALLENGE

const cache = new WeakMap();

function expensiveOperation(obj) {
if (cache.has(obj)) {
console.log('Cache hit!');
return cache.get(obj);
}

console.log('Computing result...');
const result = obj.value * 2;
cache.set(obj, result);
return result;
}

const user = { value: 42 };
expensiveOperation(user);
expensiveOperation(user);
expensiveOperation({ value: 42 });
2025/07/10 12:23:56
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