What's the output?

Question

```javascript
function* generatorOne() {
  yield ['a', 'b', 'c'];
}

function* generatorTwo() {
  yield* ['a', 'b', 'c'];
}

const one = generatorOne();
const two = generatorTwo();

console.log(one.next().value);
console.log(two.next().value);
```

Accepted Answer

With the `yield` keyword, we `yield` values in a generator function. With the `yield*` keyword, we can yield values from another generator function, or iterable object (for example an array).

In `generatorOne`, we yield the entire array `['a', 'b', 'c']` using the `yield` keyword. The value of `value` property on the object returned by the `next` method on `one` (`one.next().value`) is equal to the entire array `['a', 'b', 'c']`.

```javascript
console.log(one.next().value); // ['a', 'b', 'c']
console.log(one.next().value); // undefined
```

In `generatorTwo`, we use the `yield*` keyword. This means that the first yielded value of `two`, is equal to the first yielded value in the iterator. The iterator is the array `['a', 'b', 'c']`. The first yielded value is `a`, so the first time we call `two.next().value`, `a` is returned.

```javascript
console.log(two.next().value); // 'a'
console.log(two.next().value); // 'b'
console.log(two.next().value); // 'c'
console.log(two.next().value); // undefined
```

関連概念

What's the value of output?

What's missing?

What do we need to add to the `person` object to get `["Lydia Hallie", 21]` as the output of `[...person]`?

関連概念

関連概念

What's the value of output?

What's missing?

What do we need to add to the `person` object to get `["Lydia Hallie", 21]` as the output of `[...person]`?

関連概念