Iterating about values of an object array property

I use the Angular InMemoryService to store some fake data. I would like to transform the "HashtagDB" property into the array "hashtags". This "hashtags" array should only contain the values, but not the labels, so that I can use it to display it as Angular-Material-Chips.

As far as I understand, HashtagDB is an array property of an unnamed object. Is that correct? How do I transform the data from the array?

export class InMemoryDataService implements InMemoryDbService {
  createDb() {
    const person = [
      { Id: 1,
        HashtagsDB: [ {hashtag: 'world'}, {hashtag: 'digital'}, {hashtag: 'economy'},
    ];
    return {person};
  }
}

hashtags: string[] = [/*'world', 'digital', 'economy*/];

You can project the HashtagsDB to a string[] by using map operator.

i.e.

var people = [
  {
    ID: 1, 
    HashtagsDB: [{hashtag: 'world'}, {hashtag: 'digital'}, {hashtag: 'economy'}]
  }
];

// Hashtags of the first person.
var hashtags = people[0]['HashtagsDB'].map(item => item['hashtag']);

console.log(hashtags);
// Should returns
/*[
  "world",
  "digital",
  "economy"
]*/