Question 246684 in Javascript Question posted in
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Javascript – How to reduce one of the duplicate object from array of objects by id

I have an array of objects:

const obj = [{
  id: 1,
  name: 'A'
}, {
  id: 1,
  name: 'A'
}, {
  id: 1,
  name: 'A'
}, {
  id: 2,
  name: 'A'
}, {
  id: 2,
  name: 'A'
}]

// this method returned me one object with id=1
const filter = obj.reduce((val, index) => {
  return index === val.findIndex(v => obj.id === v.id && obj.name === o.name)
})

When I push the button I want to remove one of the duplicate object. For example I have 3 object within an array with ID=1. I want to remove only one object with ID=1 and not two. So the result must be like this:

const obj = [{
  id: 1,
  name: 'A'
}, {
  id: 1,
  name: 'A'
}, {
  id: 2,
  name: 'A'
}, {
  id: 2,
  name: 'A'
}]
Tags:

2

Answers


  1. 0

    You can achieve this by finding the index of the first object with id=1 and then using Array.prototype.splice() to remove it:

    const obj = [ { id: 1, name: 'A' }, { id: 1, name: 'A' }, { id: 1, name: 'A' }, { id: 2, name: 'A' }, { id: 2, name: 'A' } ];

const targetId = 1;
const indexToRemove = obj.findIndex(item => item.id === targetId);

if (indexToRemove !== -1) {
  obj.splice(indexToRemove, /*deleteCount=*/1);
}

console.log(obj);
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  2. 0

    Here is code that will take any number of objects and leave a maximum of two duplicates

    const filteredObj = arr.reduce((acc, curr) => {
  acc.count[curr.id] ??= 0; // conditional assignment
  acc.count[curr.id]++;
  // If the count is less than or equal to 2, add the object to the result array
  if (acc.count[curr.id] <= 2) {
    acc.result.push(curr);
  }
  return acc;
}, {
  count: {},
  result: []
}).result;

console.log(filteredObj);
    <script>
const arr = [
  { id: 1, name: 'A' },
  { id: 1, name: 'A' },
  { id: 2, name: 'B' },
  { id: 2, name: 'B' },
  { id: 3, name: 'C' },
  { id: 1, name: 'A' },
  { id: 2, name: 'B' }
];
</script>
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