JavaScript Interview questions

⭐

• Difference between == and === ?

• What is the output ?

  const d = {};
  ['zebra', 'horse'].forEach(function(k) {
  	d[k] = undefined;
  });
  // console.log(d); ?

• What is the output ?

  console.log(1 + '2' + '2');
  console.log(1 + -'1' + '2');
  console.log('A' - 'B' + '2');

⭐⭐

• What is the difference ?

  [1,2,3].map(/*() => { ... }*/);
  [1,2,3].forEach(/*() => { ... }*/);

• What is a Closure ?

  • What is a Promise ?

⭐⭐⭐

• What is the event loop ?