What is the output?
Anonymous Quiz
24%
Sarah false [object Object]
41%
Sarah true [object Object]
27%
Sarah false Person: Sarah
8%
undefined false Person: Sarah
❤5🔥4🤩3👍1
CHALLENGE
async function processData() {
console.log('Start');
const promise1 = new Promise(resolve => {
console.log('Promise 1 executor');
resolve('Result 1');
});
const promise2 = Promise.resolve('Result 2');
console.log('After promises created');
const result1 = await promise1;
console.log(result1);
const result2 = await promise2;
console.log(result2);
return 'Done';
}
processData().then(result => console.log(result));❤1
What is the output?
Anonymous Quiz
35%
Start Promise 1 executor After promises created Result 1 Result 2 Done
28%
Promise 1 executor Start After promises created Result 1 Result 2 Done
17%
Start Promise 1 executor Result 1 After promises created Result 2 Done
21%
Start After promises created Promise 1 executor Result 1 Result 2 Done
❤5👍1🔥1
The Chrome team has released an MCP server for Chrome DevTools, enabling agents like Claude Code or OpenAI Codex to use the DevTools to debug and analyze the performance and behavior of your webapps (or even just to automate the use of Chrome generally). Addy does a great job of explaining the potential here.
Addy Osmani
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❤7👍3🔥2
CHALLENGE
console.log('1');
Promise.resolve().then(() => {
console.log('2');
Promise.resolve().then(() => console.log('3'));
});
Promise.resolve().then(() => {
console.log('4');
});
setTimeout(() => console.log('5'), 0);
console.log('6');❤6👍4
“We’ve been busy,” says Cloudflare which recently announced it’s bringing Node.js HTTP server support to its Workers function platform. This post goes deep into the technicalities, covering what areas of the standard library is supported, how the file system works (Workers doesn’t have a typical file system), how input/output streams work, and more. And you can use all of this now.
James M Snell (Cloudflare)
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❤8🔥3👍1
CHALLENGE
function processData() {
try {
console.log('processing');
return 'success';
} catch (error) {
console.log('error caught');
return 'failed';
} finally {
console.log('cleanup');
}
}
const result = processData();
console.log('result:', result);🔥2
What is the output?
Anonymous Quiz
13%
error caught cleanup result: failed
50%
processing cleanup result: success
19%
processing cleanup result: undefined
19%
processing result: success cleanup
❤4👍2
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🤣11❤5👍1
CHALLENGE
class EventEmitter {
constructor() { this.events = {}; }
on(event, fn) { (this.events[event] ||= []).push(fn); }
emit(event, data) { this.events[event]?.forEach(fn => fn(data)); }
}
class Logger {
log(msg) { console.log(`LOG: ${msg}`); }
}
class Counter {
constructor() { this.count = 0; }
increment() { this.count++; console.log(this.count); }
}
function withLogging(target) {
const logger = new Logger();
return new Proxy(target, {
get(obj, prop) {
if (typeof obj[prop] === 'function') {
return function(...args) {
logger.log(`calling ${prop}`);
return obj[prop].apply(obj, args);
};
}
return obj[prop];
}
});
}
const emitter = withLogging(new EventEmitter());
const counter = new Counter();
emitter.on('tick', () => counter.increment());
emitter.emit('tick');
emitter.emit('tick');🤔6
CHALLENGE
class Animal {
constructor(name) {
this.name = name;
}
speak() {
return `${this.name} makes a sound`;
}
}
class Dog extends Animal {
speak() {
return super.speak() + ' and barks';
}
}
const pet = new Dog('Rex');
console.log(pet.speak());
console.log(pet instanceof Animal);
console.log(pet.constructor.name);❤5👍1
What is the output?
Anonymous Quiz
44%
Rex makes a sound and barks true Dog
21%
Rex barks false Dog
26%
Rex makes a sound and barks true Animal
10%
Rex makes a sound true Dog
👍10🤔1
Each year, Devographics runs an epic survey of as many JavaScript community members as it can and turns the results into an interesting report on the state of the ecosystem – here’s the results from 2024. If you have the time, fill it in, especially as they format it in a way where you can actually learn about stuff as you go.
Devographics
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❤4🤔2🔥1
CHALLENGE
class DataProcessor {
constructor(value) {
this.value = value;
}
transform(fn) {
return new DataProcessor(fn(this.value));
}
getValue() {
return this.value;
}
}
const multiply = x => x * 2;
const add = x => x + 10;
const square = x => x * x;
const result = new DataProcessor(5)
.transform(multiply)
.transform(add)
.transform(square)
.getValue();
console.log(result);❤2
❤8👍3🔥1
CHALLENGE
const Flyable = {
fly() { return 'flying'; }
};
const Swimmable = {
swim() { return 'swimming'; }
};
function mixin(Base, ...mixins) {
mixins.forEach(mixin => Object.assign(Base.prototype, mixin));
return Base;
}
class Bird {}
class Fish {}
const FlyingFish = mixin(class extends Fish {}, Flyable, Swimmable);
const instance = new FlyingFish();
console.log(instance.swim());
console.log(instance.fly());
console.log(instance instanceof Fish);What is the output?
Anonymous Quiz
20%
flying, swimming, false
48%
swimming, flying, true
24%
undefined, undefined, true
9%
swimming, flying, false
❤2🤔1
CHALLENGE
function createCounter() {
let count = 0;
return function(increment = 1) {
count += increment;
return count;
};
}
const counter1 = createCounter();
const counter2 = createCounter();
console.log(counter1());
console.log(counter1(5));
console.log(counter2(3));
console.log(counter1());
console.log(counter2());