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❤6🔥6👍5
CHALLENGE
const nums = [1, 2, 3];
const obj = { a: 1, b: 2 };
const newObj = { ...obj, b: 3, ...obj };
const arr1 = [4, 5];
const arr2 = [6, 7];
const combined = [...nums, ...arr1, ...arr2];
const [first, ...rest] = combined;
const { a, ...remaining } = newObj;
console.log(newObj.b);
console.log(rest.length);
console.log(remaining.b);
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First introduced two years ago, Node has a (still experimental) feature to build single executable applications that can be deployed to machines that don’t have Node installed. This week’s Node.js 25.5 release, with its --build-sea flag, moves the final injection step into Node itself, eliminating the need for external tooling and turning what was a multi-step, low-level process into a single command.
Joyee Cheung
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CHALLENGE
const user = {
profile: {
settings: {
theme: 'dark',
notifications: null
}
}
};
const getNotificationSound = (user) => {
return user?.profile?.settings?.notifications?.sound ?? 'default';
};
console.log(getNotificationSound(user));
console.log(getNotificationSound(null));
console.log(getNotificationSound({ profile: {} }));❤6👍6🔥3
What is the output?
Anonymous Quiz
25%
default default undefined
33%
undefined undefined undefined
14%
null default default
29%
default default default
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CHALLENGE
function processData() {
try {
console.log('start');
throw new Error('oops');
console.log('unreachable');
} catch (e) {
console.log('caught');
return 'error';
} finally {
console.log('cleanup');
}
console.log('end');
}
const result = processData();
console.log(result);🔥9❤7👍4
What is the output?
Anonymous Quiz
23%
start oops cleanup undefined
48%
start caught cleanup error
17%
start caught end error
12%
start caught cleanup undefined
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CHALLENGE
const target = { name: 'Sarah', age: 25 };
const handler = {
get(obj, prop) {
if (prop === 'toString') {
return () => `Person: ${obj.name}`;
}
return Reflect.get(obj, prop);
},
set(obj, prop, value) {
if (prop === 'age' && value < 0) {
return false;
}
return Reflect.set(obj, prop, value);
}
};
const proxy = new Proxy(target, handler);
proxy.age = -5;
proxy.location = 'NYC';
console.log(proxy.toString());
console.log(proxy.age);
console.log(proxy.location);❤9👍6🔥2
What is the output?
Anonymous Quiz
34%
Person: Sarah 25 NYC
34%
Person: Sarah undefined NYC
16%
Person: Sarah 25 undefined
16%
Person: Sarah -5 NYC
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CHALLENGE
const obj = {
name: 'Sarah',
greet() {
console.log(`Hello, ${this.name}`);
}
};
const person = { name: 'Mike' };
const func = obj.greet;
obj.greet();
func();
func.call(person);
person.hello = obj.greet;
person.hello();🔥7👍5❤3
CHALLENGE
const source = { a: 1, b: { c: 2 } };
const target1 = Object.assign({}, source);
const target2 = { ...source };
source.b.c = 99;
target1.a = 10;
target2.b.c = 50;
console.log(source.a);
console.log(source.b.c);
console.log(target1.a);
console.log(target1.b.c);
console.log(target2.a);
console.log(target2.b.c);❤5👍4🔥3
What is the output?
Anonymous Quiz
30%
1 50 10 50 1 50
29%
10 99 10 99 10 99
17%
1 2 10 2 1 2
23%
1 99 10 99 1 99
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Four stalwarts of the JavaScript ecosystem all shipped notable releases this week, and odds are you're using at least one of them:
• Gatsby v5.16 proves Gatsby, once considered neck-and-neck with Next.js in the React world, is not 'dead'. The headline feature is React 19 support.
• Babel 7 just shipped its final release. "After years in the making, Babel 8 is finally ready," in release candidate form, at least.
• Rspress 2.0 is a major release for the high-performance Rust-powered, but JavaScript-facing, static site generator.
• Lodash 4.17.23 sounds minor, but it's a 'security reset' for the still heavily used utility library and is designed to provide a base for a longer future.
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CHALLENGE
const 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;
};
};
const fibonacci = memoize((n) => {
if (n <= 1) return n;
return fibonacci(n - 1) + fibonacci(n - 2);
});
console.log(fibonacci(10));
console.log(fibonacci(5));
console.log(fibonacci(10));🔥8❤4👍2
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Why use a proper locale-aware API to parse numbers when you can hand-roll a maze of string splits, separator swaps, and implicit type coercions that silently break on edge cases?
Remy Porter (The Daily WTF)
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CHALLENGE
let counter = 0;
const increment = () => ++counter;
const getValue = () => counter;
const obj = {
get value() {
increment();
return getValue();
}
};
console.log(obj.value);
console.log(obj.value);
console.log(counter);
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