Question 352934 in Javascript Question posted in
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Javascript – How can I get the indices where array entries match a particular condition?

How can I get the indices where array entries match a particular condition?

Say, want to match device = ‘1’…

[
    { device: '1', type: 'a' },
    { device: '2', type: 'b' },
    { device: '3', type: 'c' },
    { device: '1', type: 'd' }
]

The returned result should be array [0,3].

Does JavaScript have a findIndexAll() or something like that?

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2

Answers


  1. 0

    You can create a function to do this using a combination of "map" and "indexOf", like this:

    function findIndexesByProperty(array, property, value) {
  return array.map((item, index) => item[property] === value ? index : -1)
    .filter(index => index !== -1);
}

const data = [{
    device: '1',
    type: 'a'
  },
  {
    device: '2',
    type: 'b'
  },
  {
    device: '3',
    type: 'c'
  },
  {
    device: '1',
    type: 'd'
  },
];

const indexes = findIndexesByProperty(data, 'device', '1');
console.log(indexes); // Output: [0, 3]
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  2. 0

    You can use reduce to push the indices of the matching entries into an accumulator array:

    const arr = [
    { device: '1', type: 'a' },
    { device: '2', type: 'b' },
    { device: '3', type: 'c' },
    { device: '1', type: 'd' }
]

const r = arr.reduce((a,c,i) => (c.device==='1' && a.push(i), a), [])

console.log(r)
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