Eliminate duplicate elements based on a property in a JavaScript array

Question

Eliminate duplicate elements based on a property in a JavaScript array

Looking to filter duplicates from a list of objects:

   [{name: "bob", age: "14"}, {name: "bob", age: "16"}, {name: "sue", age: "21"}]

I want to remove objects with duplicate 'name' properties, resulting in:

 [{name: "bob", age: "14"}, {name: "sue", age: "21"}]

While there are solutions for array duplicate removal, none address removing duplicates based on a specific property without considering other fields.

javascript

Answer 1

Answer №1

Traverse through the array, storing all name values in a hash and excluding objects with duplicate name values:

filterBy = function(ary, prop) {
  var seen = {};
  return ary.filter(function(item) {
    var key = item[prop];
    if(seen[key] === 1)
      return false;
    seen[key] = 1;
    return true;
  });
}

// 
a = [{name: "bob", age: "14"}, {name: "bob", age: "16"}, {name: "sue", age: "21"}]

b = filterBy(a, 'name');

console.log(b);

ES6 version:

filterBy = function(ary, prop) {
  var seen = new Set();
  return ary.filter(item => !seen.has(item[prop]) && seen.add(item[prop]));
}

a = [{name: "bob", age: "14"}, {name: "bob", age: "16"}, {name: "sue", age: "21"}]

b = filterBy(a, 'name');

console.log(b);

Answer 2

Traverse through the array, storing all name values in a hash and excluding objects with duplicate name values:

filterBy = function(ary, prop) {
  var seen = {};
  return ary.filter(function(item) {
    var key = item[prop];
    if(seen[key] === 1)
      return false;
    seen[key] = 1;
    return true;
  });
}

// 
a = [{name: "bob", age: "14"}, {name: "bob", age: "16"}, {name: "sue", age: "21"}]

b = filterBy(a, 'name');

console.log(b);

ES6 version:

filterBy = function(ary, prop) {
  var seen = new Set();
  return ary.filter(item => !seen.has(item[prop]) && seen.add(item[prop]));
}

a = [{name: "bob", age: "14"}, {name: "bob", age: "16"}, {name: "sue", age: "21"}]

b = filterBy(a, 'name');

console.log(b);

Answer 3

Answer №2

To achieve this, you can utilize 2 for loops. Simply maintain a result array and every time you add to it, verify if the name attributes match.

function findDuplicates(){
  var array= [{name: "john", age: "25"}, {name: "john", age: "30"}, {name: "lily", age: "27"}];

  var result=[];
  for(i in array){
    var found=false;
    for(j in result){
      if(result[j].name.localeCompare(array[i].name)==0){
        found=true;
      }
    }
    if(!found){
      result.push(array[i]);
    }
  }
  console.log(result);
}

Answer 4

To achieve this, you can utilize 2 for loops. Simply maintain a result array and every time you add to it, verify if the name attributes match.

function findDuplicates(){
  var array= [{name: "john", age: "25"}, {name: "john", age: "30"}, {name: "lily", age: "27"}];

  var result=[];
  for(i in array){
    var found=false;
    for(j in result){
      if(result[j].name.localeCompare(array[i].name)==0){
        found=true;
      }
    }
    if(!found){
      result.push(array[i]);
    }
  }
  console.log(result);
}

Answer 5

Answer №3

To achieve this, you can utilize the forEach method along with the thisArg parameter.

var data = [{name: "alice", age: "20"}, {name: "alice", age: "22"}, {name: "john", age: "25"}];
var result = [];

data.forEach(function(person) {
  if (!this[person.name]) {
    this[person.name] = person;
    result.push(this[person.name]);
  }
}, {});

console.log(result)

Alternatively, you can also use forEach in combination with map().

var data = [{name: "alice", age: "20"}, {name: "alice", age: "22"}, {name: "john", age: "25"}];
var result =[];

data.forEach(function(person) {
  if(result.map(item => {return item.name}).indexOf(person.name) == -1 ) result.push(person);
});

console.log(result)

Answer 6

To achieve this, you can utilize the forEach method along with the thisArg parameter.

var data = [{name: "alice", age: "20"}, {name: "alice", age: "22"}, {name: "john", age: "25"}];
var result = [];

data.forEach(function(person) {
  if (!this[person.name]) {
    this[person.name] = person;
    result.push(this[person.name]);
  }
}, {});

console.log(result)

Alternatively, you can also use forEach in combination with map().

var data = [{name: "alice", age: "20"}, {name: "alice", age: "22"}, {name: "john", age: "25"}];
var result =[];

data.forEach(function(person) {
  if(result.map(item => {return item.name}).indexOf(person.name) == -1 ) result.push(person);
});

console.log(result)

Answer 7

Answer №4

To efficiently filter out duplicate entries of the same name in an array, you can utilize the Array#filter method along with a this object for marking.

var array = [{ name: "bob", age: "14" }, { name: "bob", age: "16" }, { name: "sue", age: "21" }],
    filtered = array.filter(function (a) {
        if (!this[a.name]) {
            this[a.name] = true;
            return true;
        }
    }, Object.create(null));

console.log(filtered);

Answer 8

To efficiently filter out duplicate entries of the same name in an array, you can utilize the Array#filter method along with a this object for marking.

var array = [{ name: "bob", age: "14" }, { name: "bob", age: "16" }, { name: "sue", age: "21" }],
    filtered = array.filter(function (a) {
        if (!this[a.name]) {
            this[a.name] = true;
            return true;
        }
    }, Object.create(null));

console.log(filtered);

Answer 9

Answer №5

In the question regarding simple comparison, there are a number of great responses provided. However, if you are looking to implement a customized comparison function that can handle object values or utilize regular expressions, then consider the code snippet below.

var dedupwhen = function(fn, list){
    if(list[0] === undefined){
        return [];
    }
    // Join the first item to the remainder that has had the first
    // item filtered out (according to fn) and then been
    // deduplicated itself.
    return [list[0]].concat(dedupwhen(fn, list.slice(1).filter(function(item){
        return !fn(list[0], item);
    })));
};

var similarname = function(x,y){
    return RegExp('^' + x.name + '$', 'i').test(y.name);
};

var list = [
    {name: 'Sue', age: 44},
    {name: 'Bob', age: "14"},
    {name: 'bob', age: "16"},
    {name: 'sue', age: "21"}
];
console.log(dedupwhen(similarname, list));

Answer 10

In the question regarding simple comparison, there are a number of great responses provided. However, if you are looking to implement a customized comparison function that can handle object values or utilize regular expressions, then consider the code snippet below.

var dedupwhen = function(fn, list){
    if(list[0] === undefined){
        return [];
    }
    // Join the first item to the remainder that has had the first
    // item filtered out (according to fn) and then been
    // deduplicated itself.
    return [list[0]].concat(dedupwhen(fn, list.slice(1).filter(function(item){
        return !fn(list[0], item);
    })));
};

var similarname = function(x,y){
    return RegExp('^' + x.name + '$', 'i').test(y.name);
};

var list = [
    {name: 'Sue', age: 44},
    {name: 'Bob', age: "14"},
    {name: 'bob', age: "16"},
    {name: 'sue', age: "21"}
];
console.log(dedupwhen(similarname, list));

Eliminate duplicate elements based on a property in a JavaScript array

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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