Nested filter in typescript

Question

I have a JSON array, which looks as follows.

[
  {
        id: 1,
        name: 'Alex',
        activity: [
           {
                id: 'A1',
                status: true
            },

            {
                id: 'A2',
                status: true
            },

            {
                id: 'A3',
                status: false
            }

        ]
    },
    {
        id: 2,
        name: 'John',
        activity: [
            {
                id: 'A6',
                status: true
            },

            {
                id: 'A8',
                status: false
            },

            {
                id: 'A7',
                status: false
            }

        ]
    }
]

I want to get an array of activity id whose status should be true.I can achieve this with nester for or forEach loop. But here I am looking to achieve with the help of array functions like filter, map, and some.

I have already tried with the following.

let newArr=arr.filter(a=> a.activity.filter(b=> b.status).map(c=> c.id))

But I didn't get the correct answer Expected output

['A1','A2','A6']

Answer 1

function filter_activity(activities) {
    return activities
        && activities.length
        && activities.map(x => x.activity)
            .flat().filter(activity => activity.status)
            .map(x => x.id) || [];
}

---

Illustration

function filter_activity(activities) {
  return activities &&
    activities.length &&
    activities.map(x => x.activity)
    .flat().filter(activity => activity.status)
    .map(x => x.id) || [];
}
const input = [{
    id: 1,
    name: 'Alex',
    activity: [{
        id: 'A1',
        status: true
      },
      {
        id: 'A2',
        status: true
      },
      {
        id: 'A3',
        status: false
      }
    ]
  },
  {
    id: 2,
    name: 'John',
    activity: [{
        id: 'A6',
        status: true
      },
      {
        id: 'A8',
        status: false
      },
      {
        id: 'A7',
        status: false
      }
    ]
  }
];
console.log(filter_activity(input));

---

WYSIWYG => WHAT YOU SHOW IS WHAT YOU GET