Merge JavaScript objects with the same key value and count them

Question

I'm trying to merge objects with the same key value into one and count them. Is it even possible?

    var array = {
"items": [{
    "value": 10,
    "id": "111",
    "name": "BlackCat",
}, {
    "value": 10,
    "id": "111",
    "name": "BlackCat",
}, {
    "value": 15,
    "id": "777",
    "name": "WhiteCat",
}]
}

Desired output:

    var finalArray = {
"items": [{
    "value": 10,
    "id": "111",
    "name": "BlackCat",
    "count": 2,
}, {
    "value": 15,
    "id": "777",
    "name": "WhiteCat",
    "count": 1,
}]
}

The object "array" has 1 array inside, with 3 objetcs (like a JSON), why is that? can you modified and use just an array of objects? I think that using array.filter and map would do the trick — pmiranda, Feb 07 '17 at 14:45
Did you check this? http://stackoverflow.com/questions/33850412/merge-javascript-objects-in-array-with-same-key — pmiranda, Feb 07 '17 at 14:46

score 4 · Answer 1 · answered Feb 07 '17 at 14:46

You can use reduce on your items array:

var combinedItems = array.items.reduce(function(arr, item) {
    var found = false;

    for (var i = 0; i < arr.length; i++) {
        if (arr[i].id === item.id) {
            found = true;
            arr[i].count++;
        }
    }

    if (!found) {
        item.count = 1;
        arr.push(item);
    }

    return arr;
}, [])

Fiddle: https://jsfiddle.net/6wqw79pn/

score 0 · Answer 2 · answered Feb 07 '17 at 14:56

You could use a for loop:

var finalArray = [];
for (var i in array.items) {
  var item = array.items[i];
  var existingItem = finalArray.find(function(element){
    return (element.id == item.id);
  });
  if (!existingItem) {
    existingItem = {};
    finalArray.push(existingItem);
  } else {
    if (!existingItem.count)
      existingItem.count = 2;
    else
      existingItem.count++;
  }
  for (var j in item) {
    existingItem[j] = item[j];
  }
}

Working example: https://jsfiddle.net/mspinks/5kowbq4j/3/

score 0 · Answer 3 · answered Feb 07 '17 at 15:00

Basically you could use a hash table with the value of id as key and count.

var object = { items: [{ value: 10, id: "111", name: "BlackCat", }, { value: 10, id: "111", name: "BlackCat", }, { value: 15, id: "777", name: "WhiteCat", }] },
result = object.items.reduce(function (hash) {
    return function (r, o) {
        if (!hash[o.id]) {
            hash[o.id] = { value: o.value, id: o.id, name: o.name, count: 0 };
            r.push(hash[o.id]);
        }
        hash[o.id].count++;
        return r;
    };
}(Object.create(null)), []);
 
console.log(result);

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

Vignesh Murugan · Answer 4 · 2017-02-07T15:49:59.763

0

Underscore js will be able to solve your problem very easily

var groups = _.groupBy(array.items, function(item){
    return item.value + '#' + item.id + '#' + item.name;
});

var data = {'items' : []};

_.each(groups,function(group){
    data.items.push({
      'value' : group[0].value,
      'id' : group[0].id,
      'name' : group[0].name,
      'count' : group.length
    })
})

console.log(data)

edited Feb 07 '17 at 15:49

answered Feb 07 '17 at 15:06

Vignesh Murugan

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Merge JavaScript objects with the same key value and count them

4 Answers4