CHALLENGE
class EventManager {
constructor() {
this.listeners = new Map();
}
addListener(event, callback) {
if (!this.listeners.has(event)) {
this.listeners.set(event, new Set());
}
this.listeners.get(event).add(callback);
}
removeListener(event, callback) {
this.listeners.get(event)?.delete(callback);
}
}
const manager = new EventManager();
const handler = () => console.log('handled');
manager.addListener('click', handler);
manager.removeListener('click', () => console.log('handled'));
console.log(manager.listeners.get('click').size);What is the output?
Anonymous Quiz
19%
0
39%
TypeError: Cannot read properties of undefined of 'size'
32%
1
10%
undefined
❤3👍3🔥1
Supporting both browsers and Node.js, this library lets you read, write and convert popular media file formats (e.g. MP4, MP3, and more) without needing to lean on dependencies like FFmpeg. You can make thumbnails, extract metadata, write code that gets converted into a video, and more. GitHub repo.
Vanilagy
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CHALLENGE
const data = { a: 1, b: 2, c: 3 };
const { a, ...rest } = data;
const newObj = { ...rest, a, d: 4 };
const arr = [1, 2, 3, 4, 5];
const [first, , third, ...remaining] = arr;
const result = [...remaining, third, first];
console.log(newObj);
console.log(result);A fantastic walkthrough of Chrome’s origins and its evolution over the years. Addy looks at key milestones (multi-process architecture for example), security, its steps into the world of AI, and more.
Addy Osmani
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CHALLENGE
console.log('1');
setTimeout(() => console.log('2'), 0);
Promise.resolve().then(() => console.log('3'));
queueMicrotask(() => console.log('4'));
setTimeout(() => console.log('5'), 0);
Promise.resolve().then(() => {
console.log('6');
return Promise.resolve();
}).then(() => console.log('7'));
console.log('8');❤3
What is the output?
Anonymous Quiz
40%
1 8 3 4 6 7 2 5
25%
1 8 4 3 6 2 7 5
24%
1 8 3 6 4 7 2 5
11%
1 2 3 4 5 6 7 8