JavaScript
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CHALLENGE

const a = Math.max();
const b = Math.min();
const c = 0.1 + 0.2 === 0.3;
const d = Math.max(1, NaN, 3);
const e = [1, 2, 3].reduce((sum, n) => sum + n, 0) / 3;
const f = Number.isInteger(5.0);
console.log(a, b, c, d, e, f);
👍2
CHALLENGE

const arr = [1, [2, 3], { a: 4 }];
const copy = [...arr];
copy[1].push(99);
copy[2].a = 100;
arr[0] = 999;

console.log(arr[0], arr[1], arr[2].a, copy[0]);
👍2🔥1
CHALLENGE

function makeFns() {
const result = [];
for (var i = 0; i < 3; i++) {
let j = i;
result.push(() => i + j);
}
return result;
}
const fns = makeFns();
console.log(fns.map(f => f()).join(','));
5🔥1
What is the output?
Anonymous Quiz
28%
3,4,5
32%
3,3,3
30%
0,2,4
11%
0,1,2
4👍1
CHALLENGE

class Base {}
class Derived extends Base {
static [Symbol.hasInstance](instance) {
return false;
}
}
const d = new Derived();
console.log(d instanceof Derived, d instanceof Base, Object.getPrototypeOf(Derived) === Base);
👍3🔥21
CHALLENGE

function* inner() {
yield 1;
yield 2;
return 'inner-done';
}

function* outer() {
const result = yield* inner();
yield result;
yield 3;
}

const gen = outer();
const results = [];
let r = gen.next();
while (!r.done) {
results.push(r.value);
r = gen.next();
}
console.log(results.join(','));

export {};
5👍2🔥1
3👍2
CHALLENGE

const compose = (...fns) => x => fns.reduceRight((acc, fn) => fn(acc), x);
const pipe = (...fns) => x => fns.reduce((acc, fn) => fn(acc), x);

const inc = x => x + 1;
const double = x => x * 2;
const square = x => x * x;

const f = compose(square, double, inc);
const g = pipe(square, double, inc);

console.log(f(2), g(2));
👍4🔥21
What is the output?
Anonymous Quiz
25%
25 7
32%
9 36
32%
36 9
12%
16 5
1👍1🤩1
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🔥24🤣96🤩2👍1🤔1
CHALLENGE

const compose = (...fns) => x => fns.reduceRight((acc, fn) => fn(acc), x);
const pipe = (...fns) => x => fns.reduce((acc, fn) => fn(acc), x);

const add = n => x => x + n;
const mul = n => x => x * n;

const composed = compose(add(3), mul(2));
const piped = pipe(add(3), mul(2));

console.log(composed(5), piped(5));
🔥41
What is the output?
Anonymous Quiz
15%
10 8
36%
8 10
25%
16 13
23%
13 16
🔥21👍1
CHALLENGE

const proto = { inherited: 'nope' };
const obj = Object.create(proto);
obj.b = 2;
obj[1] = 'one';
obj.a = 1;
Object.defineProperty(obj, 'hidden', { value: 'secret', enumerable: false });
obj[Symbol('sym')] = 'symbolValue';
console.log(
Object.keys(obj).join(','),
Object.values(obj).join(','),
Object.entries(obj).length
);
👍21🔥1
1👍1🔥1
CHALLENGE

function partial(fn, ...presetArgs) {
return (...laterArgs) => fn(...presetArgs, ...laterArgs);
}

const add = (a, b, c) => a + b + c;
const addFive = partial(add, 5);
const addFiveTen = partial(addFive, 10);
console.log(addFiveTen(1), addFive(2, 3));

export {};
3🔥3👍1
What is the output?
Anonymous Quiz
17%
16 5
35%
21 10
30%
10 16
18%
16 10
🔥3👍1
CHALLENGE

const nums = [40, 100, 1, 5, 25, 10];
nums.sort();
console.log(nums.join(' '));
3🤣3