Advanced Output Traps — Series 3

Preview — 3 of 10 questions

What is logged?

javascript

const arr = [1, , 3];
const mapped = arr.map((x) => x * 2);

console.log(mapped.length, 1 in mapped, Array.from(arr), arr.filter(() => true).length);

A3 true [1, undefined, 3] 3

B3 false [1, undefined, 3] 2

C2 false [1, 3] 2

D3 false [1, NaN, 3] 3

What is logged?

javascript

const obj = {
  set only(v) {
    this._v = v;
  },
};

obj.only = 5;
console.log(obj.only, obj._v);

A5 5

B5 undefined

CTypeError: Cannot read property 'only'

Dundefined 5

What is logged?

javascript

const o = { b: 1, 2: 'two', a: 3, 1: 'one' };
console.log(Object.keys(o).join(','));

A1,2,b,a

Bb,2,a,1

C1,2,a,b

D2,1,b,a

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