What is the output?
Anonymous Quiz
30%
function function function function
36%
undefined undefined function function
13%
function undefined function function
22%
undefined function function function
👍5❤2🔥2
What’s New? — It’s that time of year again. The Ecma General Assembly has approved the ES2025 language specification, which you can read in full here if you have a gallon of coffee to hand — or you can enjoy Dr. Axel’s more succinct explainer instead.
Dr. Axel Rauschmayer
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❤7👍3🔥2🤔1
CHALLENGE
const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
const result = numbers
.filter(num => num % 2 === 0)
.map(num => num * 2)
.reduce((acc, curr, idx, arr) => {
if (idx === arr.length - 1) {
return (acc + curr) / arr.length;
}
return acc + curr;
}, 0);
console.log(result);
❤8👍1
Dr. Axel asks us to imagine if we had to write JavaScript without any whitespace or comments, so why should we have to write regexes that way? He has some tips for making the process more pleasant.
Dr. Axel Rauschmayer
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❤7🔥2🤔2👍1
CHALLENGE
const cache = new WeakMap();
const user1 = { name: 'Alice' };
const user2 = { name: 'Bob' };
cache.set(user1, { lastLogin: 'yesterday' });
cache.set(user2, { lastLogin: 'today' });
const result = [];
result.push(cache.has(user1));
result.push(cache.get(user2).lastLogin);
let user3 = { name: 'Charlie' };
cache.set(user3, { lastLogin: 'now' });
result.push(cache.has(user3));
user3 = null; // Removing the reference
// Garbage collector might run here in real situations
const user4 = { name: 'Charlie' }; // Same name, different object
result.push(cache.has(user4));
console.log(result);
❤5
What is the output?
Anonymous Quiz
24%
[false, 'today', true, false]
40%
[true, 'today', true, false]
17%
[true, undefined, true, false]
19%
[true, 'today', true, true]
👍8🔥3❤1
CHALLENGE
const items = ['apple', 'banana', 'cherry', 'date'];
const result = items
.map(item => item.toUpperCase())
.filter(item => item.length > 5)
.reduce((acc, item, index) => {
return acc + (index === 0 ? '' : '-') + item.slice(0, 3);
}, '');
console.log(result);
❤2
What is the output?
Anonymous Quiz
27%
BANANA-CHERRY-DATE
45%
BAN-CHE
20%
BANANA-CHERRY
8%
BAN-CHE-DAT
🔥9🤔2❤1
Hono is a framework well worth exploring. It’s fast, lightweight, built on Web Standards, and can be used to build apps that work on numerous platforms from Node or Bun to Cloudflare or Fastly. v4.8 adds new route helper functions, improvements to JSX streaming and CORS, a new plugin system for static site generation, and more.
Yusuke Wada and Contributors
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❤7👍1🔥1
CHALLENGE
const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
const result = numbers
.filter(n => n % 2 === 0)
.map(n => n * 2)
.reduce((acc, curr, idx, arr) => {
if (idx === arr.length - 1) {
return (acc + curr) / arr.length;
}
return acc + curr;
}, 0);
console.log(result);
❤2🔥2🤔2
🤔8🤣3❤2
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
What is the output?
Anonymous Quiz
44%
Clippers 2 100
25%
Lakers 2 100
20%
Lakers 3 42
11%
Clippers 3 100
❤3👍3🔥3
CHALLENGE
let x = 5;
function foo() {
console.log(x);
let x = 10;
console.log(x);
}
foo();
❤1
What is the output?
Anonymous Quiz
25%
ReferenceError: Cannot access 'x' before initialization
26%
undefined 10
13%
5 ReferenceError: x is not defined
36%
5 10
❤8👍4🤣3🔥2
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);
❤4
What is the output?
Anonymous Quiz
22%
3 4 undefined undefined
22%
3 3 Seattle undefined
45%
3 4 Seattle undefined
11%
4 4 Seattle Seattle
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