What is the best way to eliminate a duplicate key-value pair from a JSON array?

Question

What is the best way to eliminate a duplicate key-value pair from a JSON array?

Consider the following JSON data:

[{"name": "John", "id": 1},
 {"name": "Don", "id": 2},
 {"name": "Tom", "id": 3},
 {"name": "NewJohn", "id": 1},
 {"name": "Tim", "id": 4}]

I'm looking to determine if the key "id" has duplicate values. If duplicates are found, I want to remove the earlier instances of the JSON with the same "id" in order to obtain a modified JSON Array with unique "id" values.

[{"name": "Don", "id": 2},
 {"name": "Tom", "id": 3},
 {"name": "NewJohn", "id": 1},
 {"name": "Tim", "id": 4}]

Is there a JavaScript solution for achieving this?

javascript arrays json arraylist

Answer 1

Answer №1

If you want to iterate through an array from the end and only add unique elements based on a specific criteria, you can utilize the reduceRight method.

var data = [{"name": "John", "id": 1}, {"name": "Don", "id": 2}, {"name": "Tom", "id": 3}, {"name": "NewJohn", "id": 1}, {"name": "Tim", "id": 4}]

var result = [] 
data.reduceRight(function(r, e) {
  if(!r[e.id]) {
    result.unshift(e);
    r[e.id] = 1;
  }
  return r;
}, {})

console.log(result)

Answer 2

If you want to iterate through an array from the end and only add unique elements based on a specific criteria, you can utilize the reduceRight method.

var data = [{"name": "John", "id": 1}, {"name": "Don", "id": 2}, {"name": "Tom", "id": 3}, {"name": "NewJohn", "id": 1}, {"name": "Tim", "id": 4}]

var result = [] 
data.reduceRight(function(r, e) {
  if(!r[e.id]) {
    result.unshift(e);
    r[e.id] = 1;
  }
  return r;
}, {})

console.log(result)

Answer 3

Answer №2

Try this code snippet for a solution to your issue:

var dataArray = [{"name": "John", "id": 1}, {"name": "Don", "id": 2}, {"name": "Tom", "id": 3}, {"name": "NewJohn", "id": 1}, {"name": "Tim", "id": 4}];
    var seenIds = {};

dataArray = dataArray.reverse().filter(function(currentItem) {
    if (currentItem.id in seenIds) {
        return false;
    } else {
        seenIds[currentItem.id] = true;
        return true;
    }
});

console.log(dataArray)

Answer 4

Try this code snippet for a solution to your issue:

var dataArray = [{"name": "John", "id": 1}, {"name": "Don", "id": 2}, {"name": "Tom", "id": 3}, {"name": "NewJohn", "id": 1}, {"name": "Tim", "id": 4}];
    var seenIds = {};

dataArray = dataArray.reverse().filter(function(currentItem) {
    if (currentItem.id in seenIds) {
        return false;
    } else {
        seenIds[currentItem.id] = true;
        return true;
    }
});

console.log(dataArray)

Answer 5

Answer №3

let newMap = createMap(data.map(item => [item.id, item]));

You have the option to convert it into a Map.. and then destructure it into an array:

newMap = [...newMap].map(element => element[1]);

http://jsbin.com/zuqabonebe/edit?console

Answer 6

let newMap = createMap(data.map(item => [item.id, item]));

You have the option to convert it into a Map.. and then destructure it into an array:

newMap = [...newMap].map(element => element[1]);

http://jsbin.com/zuqabonebe/edit?console

Answer 7

Answer №4

Through the use of two nested for loops, I am able to remove the duplicate id property from a given set of data.

var data=[{"name": "John", "id": 1},
 {"name": "Don", "id": 2},
 {"name": "Tom", "id": 3},
 {"name": "NewJohn", "id": 1},
 {"name": "Tim", "id": 4}];

function deleteJsonProperty(dataJson){
for(var i=0;i<dataJson.length;i++){  
  for(var z=i+1;z<dataJson.length;z++){
  if(dataJson[i].id===dataJson[z].id){
    delete dataJson[i].id;
  }
  }
}
  return dataJson;
}
console.log(deleteJsonProperty(data));

Answer 8

Through the use of two nested for loops, I am able to remove the duplicate id property from a given set of data.

var data=[{"name": "John", "id": 1},
 {"name": "Don", "id": 2},
 {"name": "Tom", "id": 3},
 {"name": "NewJohn", "id": 1},
 {"name": "Tim", "id": 4}];

function deleteJsonProperty(dataJson){
for(var i=0;i<dataJson.length;i++){  
  for(var z=i+1;z<dataJson.length;z++){
  if(dataJson[i].id===dataJson[z].id){
    delete dataJson[i].id;
  }
  }
}
  return dataJson;
}
console.log(deleteJsonProperty(data));

What is the best way to eliminate a duplicate key-value pair from a JSON array?

Answer №1

Answer №2

Answer №3

Answer №4

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