Engine-Level Behaviour — Series 3

Preview — 3 of 10 questions

What is logged?

javascript

const o = { b: 1, 2: 'a', '-1': 'neg', 1.5: 'f', 1: 'one', a: 2 };
console.log(Object.keys(o).join('|'));

Ab|2|-1|1.5|1|a

B-1|1|1.5|2|a|b

C1|2|b|-1|1.5|a

D1|1.5|2|b|-1|a

What is logged? (Sloppy mode.)

javascript

const s = 'abc';
s.foo = 1;

console.log(s.foo, typeof s, Object.getOwnPropertyNames(Object('abc')).join(','));

Aundefined string 0,1,2,length

B1 string 0,1,2,length

Cundefined object 0,1,2

D1 object length

What is logged?

javascript

try {
  console.log(1n + 1);
} catch (e) {
  console.log(e.constructor.name);
}
console.log(1n == 1, 1n === 1, typeof (1n * 2n));

A2 true true bigint

B2n true false bigint

CRangeError true false number

DTypeError true false bigint

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