CODEWITHSUNDEEP
javascriptarrayscount
kree
kree

Reputation: 449

Store the occurrence in an array

I'm looking for an effective way to count the occurrence of elements. I read the data in a loop, and in every step I want to increase the right object element in the result array, or create a new one, if it isn't available yet.

I have to work with a lot of data, so I need a quick solution. Here is a working version:

var hugeDataObject = [
    {id: '1234', dark: true},
    {id: '5678', dark: true},
    {id: '91011', dark: true},
    {id: '91011', dark: false}
];
var ids = [];
var darks = [];
var allIds = [];
var allDarks = [];
  hugeDataObject.forEach(function(attrs) {
    var index = allIds.indexOf(attrs.id);
    if(index >= 0) ids[index].amount += 1;
    else {
      ids.push({type: attrs.id, amount: 1}); 
      allIds.push(attrs.id);
    }

    var index = allDarks.indexOf(attrs.dark);
    if(index >= 0) darks[index].amount += 1;
    else {
      darks.push({type: attrs.dark, amount: 1}); 
      allDarks.push(attrs.dark);
    }
  });

Fiddle But I have more types, what I need to count, so there is too much variable.

The result: 

ids = [
  {type: '1234', amount: 1},
  {type: '5678', amount: 1},
  {type: '91011', amount: 2}
]

darks = [
  {type: true, amount: 3},
  {type: false, amount: 1}
]

(If you use loDash, it's ok)

Thanks in advance!

Upvotes: 0

Views: 75

Answers (4)

kree
kree

Reputation: 449

It's not too simple, but I got it.

var getObjectBy = function(base, id, array) {
    for (var i = 0, len = array.length; i < len; i++) {
        if (array[i][base] === id) return array[i];
    }
    return null;
};

var hugeDataObject = [
    {id: '1234', dark: true},
    {id: '5678', dark: true},
    {id: '91011', dark: true},
    {id: '91011', dark: false}
];
var ids = [];
var darks = [];
hugeDataObject.forEach(function(attrs) {
    var index = getObjectBy('type', attrs.id, ids);
    if (index === null) ids.push({type: attrs.id, amount: 1});
    else index.amount += 1;

    var index = getObjectBy('type', attrs.dark, darks);
    if (index === null) darks.push({type: attrs.dark, amount: 1});
    else index.amount += 1;
});

Updated Fiddle

Perhaps it isn't too pretty, but I think effective. If you know a better way, write it, and I will accept that!

Thanks your answers guys!

Upvotes: -1

Sergey Metlov
Sergey Metlov

Reputation: 26291

var counter = {};
hugeDataObject.forEach(function(attrs) {
    if (counter[attrs.id]) {
        counter[attrs.id]++;
    }
    else {
        counter[attrs.id] = 1;
    }
});

Or if you need array:

var counts = [];
var indexMap = {};

var i = 0;
indexMap[0] = -1;

hugeDataObject.forEach(function(attrs) {

    var index = indexMap[attrs.id];

    if (index == undefined) {
        indexMap[attrs.id] = i;
        counts[i] = { id: attrs.id, amount: 1 };
        i++;
    }
    else {
        var existingCounter = counts[index];
        existingCounter.amount++;
    }
});

Upvotes: 1

AmanVirdi
AmanVirdi

Reputation: 1685

If I understand your point, then you try use this:

 var ids = [];
  var allIds = [];
  hugeDataObject.forEach(function(attrs) {
    var index = allIds.indexOf(attrs.id);
    if(index >= 0){
      ids[index].amount = ids[index].amount + 1;

    } else {
      ids.push({type: attrs.id, amount: 1}); 
      allIds.push(attrs.id);
      // Here first should check is this type available, 
      // after create it or increase the amount
    }
  });

  console.log(ids);

Upvotes: 0

Wolph
Wolph

Reputation: 80011

How about a simpler structure to store:

var objects = {};
objects['id1234'] = 384;
objects['id5678'] = 955;
objects['id91011'] = 1510;

/* increment */
objects['id1234']++;

Upvotes: 1

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