Remove duplicate objects from an array with Keys

Question

How to filter array of objects by property? for example in this array if two or more objects have same properties like name and lastname I want to remove either of them and leave only unique one in an array. example arr:

    [ {name: "George", lastname: "GeorgeLast", age: 12},
      {name: "George", lastname: "GeorgeLast", age: 13},
      {name: "Bob", lastname: "GeorgeLast", age: 12}]

result should be either

 [ {name: "George", lastname: "GeorgeLast", age: 13},
   {name: "Bob", lastname: "GeorgeLast", age: 12}]

or

 [ {name: "George", lastname: "GeorgeLast", age: 12},
   {name: "Bob", lastname: "GeorgeLast", age: 12}]

score 2 · Accepted Answer · answered Jan 03 '22 at 14:44

Apply the technique shown in this answer, which is:

function onlyUnique(value, index, self) {
  return self.indexOf(value) === index;
}

...but using findIndex with some criteria rather than just indexOf.

let people = [
  { name: "George", lastname: "GeorgeLast", age: 12 },
  { name: "George", lastname: "GeorgeLast", age: 13 },
  { name: "Bob", lastname: "GeorgeLast", age: 12 }
]

let result = people.filter(
  (person, index) => index === people.findIndex(
    other => person.name === other.name
      && person.lastname === other.lastname
  ));
console.log(result);

As for whether it keeps 12-year-old George or 13-year-old George, it is a matter of how findIndex works, which so happens to return the first matching element. So in your example case it will keep 12-year-old George.

Nazeh Taha · Answer 2 · 2022-09-12T10:10:48.817

The Map object holds key-value pairs and remembers the original insertion order of the keys.

   const arr = [
    { name: "George", lastname: "GeorgeLast", age: 12 },
    { name: "George", lastname: "GeorgeLast", age: 13 },
    { name: "Bob", lastname: "GeorgeLast", age: 12 }
    ];
    
    const newMap = new Map();
    arr.forEach((item) => newMap.set(item.name, item));
    console.log([...newMap.values()]);

score 0 · Answer 3 · answered Jan 03 '22 at 15:06

Another solution.
Here you don't need to iterate through the list n*n/2 times (if I count correctly).
On the other hand, this one looks less concise and uses more memory.
Use whichever you prefer.

const arr = [
  {name: "George", lastname: "GeorgeLast", age: 12},
  {name: "George", lastname: "GeorgeLast", age: 13},
  {name: "Bob", lastname: "GeorgeLast", age: 12}
];

const obj = {}
arr.forEach(v => {
  if (!obj[v.name]) {
    obj[v.name] = {}
  }
  if (!obj[v.name][v.lastname]) {
    obj[v.name][v.lastname] = v;
  }
})

const result = [];
Object.values(obj).forEach(nameObj =>
  Object.values(nameObj).forEach(surnObj => result.push(surnObj))
);

console.log(result)

Remove duplicate objects from an array with Keys

3 Answers3