Regular expression named capture groups

I saw this tweet today and wanted to dig a little deeper into the destructuring assignment...

The capture group is composed by putting everything in the group between parens, and naming it with ?<name>

so year alone would like this:

const year = /(?<year>\d{4})/

The destructuring part of the tweet and Axel's follow-up, I found confusing. How can I destructure it as both an object and array?

const [match, year, month, day] = re.exec('2021-03-04');

Looking at the object keys helped clear things up:

console.log("'re' object keys:",Object.keys(re.exec('2021-03-04')));

gives me:

["0","1","2","3","index","input","groups"]

Code can be found here:
Codepen