JavaScript · Middle · Question 4 of 75

What does this code print after a second?

const timer = {
  seconds: 10,
  start() {
    setTimeout(function () { console.log(this.seconds); }, 1000);
  },
};
timer.start();

✓Correct answer: undefined: a regular callback function has its own this
210: the callback gets this from the start method
3ReferenceError: this is unavailable inside a timer

Explanation

The timer calls the callback without a context, so this isn't timer. An arrow function () => console.log(this.seconds) would take this from start and print 10. This is the classic case where arrows are useful.

What does this code print after a second?

Explanation

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