How can we invoke `sum` in `sum.js` from `index.js?`

Question

```javascript
// sum.js
export default function sum(x) {
  return x + x;
}

// index.js
import * as sum from './sum';
```

Accepted Answer

With the asterisk `*`, we import all exported values from that file, both default and named. If we had the following file:

```javascript
// info.js
export const name = 'Lydia';
export const age = 21;
export default 'I love JavaScript';

// index.js
import * as info from './info';
console.log(info);
```

The following would get logged:

```javascript
{
  default: "I love JavaScript",
  name: "Lydia",
  age: 21
}
```

For the `sum` example, it means that the imported value `sum` looks like this:

```javascript
{ default: function sum(x) { return x + x } }
```

We can invoke this function, by calling `sum.default`

関連概念