How to filter nested arrays (composing JS filters) [duplicate]

Question

A am trying to return a new array that is filtered on sub-properties of objects.

I am trying to nest two filters together to achieve this result.

let header = "xyz";

let data = [{
  "header": header,
  items: [{
    id: 1,
    status: "Y"
  }, {
    id: 2,
    status: "N"
  }, {
    id: 3,
    status: "N"
  }]
},{
  "header": header,
  items: [{
    id: 1,
    status: "N"
  }, {
    id: 2,
    status: "Y"
  }]
}];

let result = data.filter(item => {
  return item.items.filter(item => {
    return item.status === "Y";
  })
});

Expected output

[{
  "header": header,
  items: [{
    id: 1,
    status: "Y"
  }]
},{
  "header": header,
  items: [{
    id: 2,
    status: "Y"
  }]
}];

How can I filter the original array where status === 'Y'?

Yeah, your inner filter returns an empty array which is evaluated to true, so nothing gets filtered. Add .length to the inner filter or use .some. — ggorlen
– ggorlen, Commented Jun 24, 2019 at 18:11
.some returns { id: 1, status: 'Y' }, { id: 1, status: 'N' }, { id: 2, status: 'Y' } — ang
– ang, Commented Jun 24, 2019 at 18:17

Bali Balo · Accepted Answer · 2019-06-24 18:13:44Z

2

You could map first to get an equivalent array with filtered sub-items, then filter the main array to remove the elements with no sub-items.

let result = data.map(item => {
    return {
        header: item.header,
        items: item.items.filter(subItem => subItem.status === 'Y')
    };
}).filter(item => item.items.length);

answered Jun 24, 2019 at 18:13

Bali Balo

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Comments

Naga Sai A · Accepted Answer · 2019-06-24 18:19:16Z

1

To achieve expected result, use below option of using reduce

Loop data using reduce
Update each object.items before pushing to accumulator-acc of reduce

working code

let header = "xyz";

let data = [{
  "header": header,
  items: [{
    id: 1,
    status: "Y"
  }, {
    id: 2,
    status: "N"
  }, {
    id: 3,
    status: "N"
  }]
},{
  "header": header,
  items: [{
    id: 1,
    status: "N"
  }, {
    id: 2,
    status: "Y"
  }]
}];

console.log(data.reduce((acc,v) => {
  v. items = v.items.filter(item => {
    return item.status === "Y";
  })
  acc.push(v)
   return acc
}, []))

codepen - https://codepen.io/nagasai/pen/EBXvLx

answered Jun 24, 2019 at 18:19

Naga Sai A

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