What is the output?
Anonymous Quiz
26%
10 4 6 Not found
28%
10 4 3 undefined
37%
20 4 6 Not found
8%
20 4 3 Not found
👍3🔥2❤1
JavaScript (originally named LiveScript) turns thirty years old this year and the Deno team has put together a fantastic timeline-based tour of how much things have progressed from its first appearance in Netscape Navigator, through offshoots like JScript, standardization, and the introduction of Node.js, all the way through to the modern day.
The Deno Team
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❤12👍2🔥1
CHALLENGE
function analyze(...items) {
const [first, ...rest] = items;
const { length } = [...rest, 'bonus'];
const result = {
...first,
count: length,
};
console.log(result);
}
analyze({ id: 42, name: 'Item' }, 'a', 'b');What is the output?
Anonymous Quiz
20%
{ id: 42, count: 3 }
34%
{ id: 42, name: 'Item', count: 2 }
41%
{ id: 42, name: 'Item', count: 3 }
5%
{ count: 3 }
🔥4❤3👍1
CHALLENGE
const user = { id: 1, name: 'Alice' };
const userData = new WeakMap();
userData.set(user, { lastLogin: '2023-01-01' });
const clone = { ...user };
const originalData = userData.get(user);
const cloneData = userData.get(clone);
console.log(originalData, cloneData);❤1👍1
Two members of the Angular team presented a session at this week’s Google I/O event on the latest updates to the Angular framework in anticipation of the eventual release of Angular 20 next Thursday.
Chasanoff and Thompson (Google)
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🔥4👍2
CHALLENGE
function mystery() {
try {
throw new Error('Oops');
return 'A';
} catch (err) {
return 'B';
} finally {
return 'C';
}
}
function wrapper() {
try {
return mystery();
} finally {
console.log('D');
}
}
console.log(wrapper());👍7
🔥3❤2👍2
CHALLENGE
function compose(...funcs) {
return function(x) {
return funcs.reduceRight((acc, fn) => fn(acc), x);
};
}
const add10 = x => x + 10;
const multiply2 = x => x * 2;
const toString = x => `Result: ${x}`;
const composed = compose(toString, multiply2, add10);
console.log(composed(5));👍6❤1
👍7🤔4❤2🔥2
CHALLENGE
try {
try {
// Creating a custom error type
class CustomError extends Error {
constructor(message) {
super(message);
this.name = "CustomError";
}
}
const fn = () => {
throw new CustomError("Something went wrong");
};
try {
fn();
} catch (e) {
throw new TypeError("Type error occurred");
}
} catch (e) {
console.log(e instanceof Error, e.name, e instanceof TypeError);
}
} catch (e) {
console.log("Outer catch", e.message);
}❤5👍2🔥1
What is the output?
Anonymous Quiz
30%
true 'CustomError' false
32%
true 'TypeError' false
20%
false 'CustomError' false
18%
true 'TypeError' true
❤3👍3🔥2
CHALLENGE
function* counter() {
let i = 1;
while (true) {
const reset = yield i++;
if (reset) {
i = 1;
}
}
}
const gen = counter();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next(true).value);
console.log(gen.next().value);❤2
What is the output?
Anonymous Quiz
31%
1, 2, 1, 2
34%
1, 2, undefined, 1
20%
1, 2, 1, 1
14%
1, 2, 3, 4
👍8❤2
CHALLENGE
const users = [
{ id: 1, name: 'Alice' },
{ id: 2, name: 'Bob' },
{ id: 3, name: 'Charlie' }
];
const userScores = new WeakMap();
// Set scores for users
userScores.set(users[0], 95);
userScores.set(users[1], 80);
// Remove reference to Bob
users[1] = null;
let sum = 0;
for (const user of users) {
if (user && userScores.has(user)) {
sum += userScores.get(user);
}
}
console.log(sum);
👍7❤2
What is the output?
Anonymous Quiz
22%
Error: Invalid value used as weak map key
30%
175
35%
95
12%
undefined
❤4🔥1
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🤔11🤣8👍4
CHALLENGE
class ShoppingCart {
constructor() {
if (ShoppingCart.instance) {
return ShoppingCart.instance;
}
this.items = [];
ShoppingCart.instance = this;
}
addItem(item) {
this.items.push(item);
}
getItems() {
return [...this.items];
}
}
const cart1 = new ShoppingCart();
const cart2 = new ShoppingCart();
cart1.addItem('Book');
cart2.addItem('Laptop');
console.log(cart1.getItems());❤3