Filtering out customized repetitive objects from an array using JavaScript

Question

Filtering out customized repetitive objects from an array using JavaScript

Given an array of objects like the one below, I need to selectively filter out repetitive keys in order to address specific duplicates without removing all instances.

var arr = [
    {id: 1, value: 'John'},
    {id: 2, value: 'John'}, // Should be filtered
    {id: 3, value: 'John'}, // Should be filtered
    {id: 4, value: 'John'}, // Should be filtered
    {id: 5, value: 'Alex'},
    {id: 6, value: 'Louis'},
    {id: 7, value: 'David'},
    {id: 8, value: 'David'}, // Should not be filtered

]

Desired Result:

arr = [
    {id: 1, value: 'John'},
    {id: 5, value: 'Alex'},
    {id: 6, value: 'Louis'},
    {id: 7, value: 'David'},
    {id: 8, value: 'David'},

]

I have attempted the following solution so far:

arr = arr.reduce((a, b) => {
    if (!a.some(x => x.description === b.description)) a.push(b);
    return a;
}, []);

Thank you in advance.

javascript arrays

Answer 1

Answer №1

If you're interested in removing duplicates and maintaining the first item, one way to do this is by using a closure with a Set for filtering.

const
    array = [{ id: 1, value: 'John' }, { id: 2, value: 'John' }, { id: 3, value: 'John' }, { id: 4, value: 'John' }, { id: 5, value: 'Alex' }, { id: 6, value: 'Louis' }, { id: 7, value: 'David' }, { id: 8, value: 'David' }],
    keep = ['David'],
    result = array.filter(
        (s => ({ value }) => keep.includes(value) || !s.has(value) && s.add(value))
        (new Set)
    );

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

If you're interested in removing duplicates and maintaining the first item, one way to do this is by using a closure with a Set for filtering.

const
    array = [{ id: 1, value: 'John' }, { id: 2, value: 'John' }, { id: 3, value: 'John' }, { id: 4, value: 'John' }, { id: 5, value: 'Alex' }, { id: 6, value: 'Louis' }, { id: 7, value: 'David' }, { id: 8, value: 'David' }],
    keep = ['David'],
    result = array.filter(
        (s => ({ value }) => keep.includes(value) || !s.has(value) && s.add(value))
        (new Set)
    );

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 3

Answer №2

Implementing a solution using the Set data structure along with an array or set containing exceptions.

var items = [
    {id: 1, name: 'John'},
    {id: 2, name: 'John'}, // Should be excluded
    {id: 3, name: 'John'}, // Should be excluded
    {id: 4, name: 'John'}, // Should be excluded
    {id: 5, name: 'Alex'},
    {id: 6, name: 'Louis'},
    {id: 7, name: 'David'},
    {id: 8, name: 'David'}, // Should not be excluded

]

const filterDuplicates = (items, exceptions) => {
  const values = new Set();
  return items.filter(item => {
    if(values.has(item.name) && !exceptions.includes(item.name)){
      return false;
    } else {
      values.add(item.name);
      return true;
    }
  })
}

console.log(filterDuplicates(items, ["David"]));

Answer 4

Implementing a solution using the Set data structure along with an array or set containing exceptions.

var items = [
    {id: 1, name: 'John'},
    {id: 2, name: 'John'}, // Should be excluded
    {id: 3, name: 'John'}, // Should be excluded
    {id: 4, name: 'John'}, // Should be excluded
    {id: 5, name: 'Alex'},
    {id: 6, name: 'Louis'},
    {id: 7, name: 'David'},
    {id: 8, name: 'David'}, // Should not be excluded

]

const filterDuplicates = (items, exceptions) => {
  const values = new Set();
  return items.filter(item => {
    if(values.has(item.name) && !exceptions.includes(item.name)){
      return false;
    } else {
      values.add(item.name);
      return true;
    }
  })
}

console.log(filterDuplicates(items, ["David"]));

Answer 5

Answer №3

To determine if a value has already been encountered, you can utilize Array#filter along with a boolean indicator.

var data = [
    {id: 1, value: 'Alice'},
    {id: 2, value: 'Alice'}, // Should be removed
    {id: 3, value: 'Alice'}, // Should be removed
    {id: 4, value: 'Alice'}, // Should be removed
    {id: 5, value: 'Bob'},
    {id: 6, value: 'Charlie'},
    {id: 7, value: 'David'},
    {id: 8, value: 'David'}, // Should not be removed
];
const filterDuplicates = (data, val)=>{
  let check = false;
  return data.filter(({value})=>value !== val || (!check && (check = true)));
};
console.log(filterDuplicates(data, 'Alice'));

Answer 6

To determine if a value has already been encountered, you can utilize Array#filter along with a boolean indicator.

var data = [
    {id: 1, value: 'Alice'},
    {id: 2, value: 'Alice'}, // Should be removed
    {id: 3, value: 'Alice'}, // Should be removed
    {id: 4, value: 'Alice'}, // Should be removed
    {id: 5, value: 'Bob'},
    {id: 6, value: 'Charlie'},
    {id: 7, value: 'David'},
    {id: 8, value: 'David'}, // Should not be removed
];
const filterDuplicates = (data, val)=>{
  let check = false;
  return data.filter(({value})=>value !== val || (!check && (check = true)));
};
console.log(filterDuplicates(data, 'Alice'));

Answer 7

Answer №4

let array = [
  { id: 1, value: "John" },
  { id: 2, value: "John" }, // Filtered out
  { id: 3, value: "John" }, // Filtered out
  { id: 4, value: "John" }, // Filtered out
  { id: 5, value: "Alex" },
  { id: 6, value: "Louis" },
  { id: 7, value: "David" },
  { id: 8, value: "David" }, // Should not be filtered
];

const filteredArray = Array.from(
  array.reduce((filtered, item) => {
    if (!filtered.has(item.value)) {
      filtered.set(item.value, item);
    }
    return filtered;
  }, new Map()).values()
);

console.log(filteredArray);

Answer 8

let array = [
  { id: 1, value: "John" },
  { id: 2, value: "John" }, // Filtered out
  { id: 3, value: "John" }, // Filtered out
  { id: 4, value: "John" }, // Filtered out
  { id: 5, value: "Alex" },
  { id: 6, value: "Louis" },
  { id: 7, value: "David" },
  { id: 8, value: "David" }, // Should not be filtered
];

const filteredArray = Array.from(
  array.reduce((filtered, item) => {
    if (!filtered.has(item.value)) {
      filtered.set(item.value, item);
    }
    return filtered;
  }, new Map()).values()
);

console.log(filteredArray);

Filtering out customized repetitive objects from an array using JavaScript

Answer №1

Answer №2

Answer №3

Answer №4

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