How to filter an array based on property value and return array of objects

Question

I have this array of objects with the name and isPinned keys. I would like to store only the country name in a new array based on what isPinned is. For example, if Australia and China have isPinned as true, then the new array would be:

const countriesFiltered = ["Australia", "China"]

const countries = [
    { name: "Australia", isPinned: true },
    { name: "China", isPinned: true },
    { name: "India", isPinned: false },
  ];

Answer 1

You would .filter by isPinned and then .map by name

const namesOfPinnedCountries = countries
    .filter(it => it.isPinned)
    .map(it => it.name)

Answer 2

.filter() and .map() is the classical solution, but you can also do it with .reduce() :

 const countries = [ { name: "Australia", isPinned: true }, { name: "China", isPinned: true }, { name: "India", isPinned: false }, ]; const res=countries.reduce((a,c)=> c.isPinned?[...a,c.name]:a,[]); console.log(res);

Answer 3

You can use flatMap :

 const countries = [ { name: "Australia", isPinned: true }, { name: "China", isPinned: true }, { name: "India", isPinned: false }, ]; const countriesFiltered = countries.flatMap(i => i.isPinned? i.name: []); console.log(countriesFiltered);