How to count duplicate value in an array and store in array

Question

I have some array of objects and in that few data. My input is like :

My actual code is :

buildcount: function(store2){
   var datacount = store2.data.items;
    for(var i=0; i<datacount.length; i++){
        var x = datacount[i].data
},

Here from store I am hgetting x which is array of object and each object have

obj{
    STU: "Study1", SUB: "Subject1", EXL: "Yes"}
}

Object {STU: "Study1", SUB: "Subject1", EXL: "Yes"}
Object {STU: "Study1", SUB: "Subject1", EXL: "Yes"}
Object {STU: "Study2", SUB: "Subject1", EXL: "Yes"}
Object {STU: "Study3", SUB: "Subject1", EXL: "Yes"}
Object {STU: "Study1", SUB: "Subject1", EXL: "Yes"}
Object {STU: "Study3", SUB: "Subject1", EXL: "Yes"}
Object {STU: "Study3", SUB: "Subject1", EXL: "Yes"}
Object {STU: "Study2", SUB: "Subject1", EXL: "Yes"}

I want to count all the unique element and store in array with count. In javascript.

Output : object {"Study1 : 3", "Study2" : 2, "Study3":4}

What have you tried so far? Please share it. I can't see how you retrieve these objects as input. — scriptmonster
– scriptmonster, Commented Jul 3, 2016 at 12:16
Given your input dataset, the correct output would be object {"Study1 : 3", "Study2" : 2, "Study3":3} — Arnauld
– Arnauld, Commented Jul 3, 2016 at 12:21

Nenad Vracar · Accepted Answer · 2016-07-03 12:27:31Z

2

You can do this with reduce

var ar =  [{"STU":"Study1","SUB":"Subject1","EXL":"Yes"},{"STU":"Study1","SUB":"Subject1","EXL":"Yes"},{"STU":"Study2","SUB":"Subject1","EXL":"Yes"},{"STU":"Study3","SUB":"Subject1","EXL":"Yes"},{"STU":"Study1","SUB":"Subject1","EXL":"Yes"},{"STU":"Study3","SUB":"Subject1","EXL":"Yes"},{"STU":"Study3","SUB":"Subject1","EXL":"Yes"},{"STU":"Study2","SUB":"Subject1","EXL":"Yes"}]

var result = ar.reduce(function(o, e) {
  return o[e.STU] = (o[e.STU] || 0) + 1, o
}, {});

console.log(result)

answered Jul 3, 2016 at 12:27

Nenad Vracar

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4 Comments

David Over a year ago

Do I need to write reduce function anywhere.

Nenad Vracar Over a year ago

I am not sure what do you mean by that?

David Over a year ago

I am using EXTjs framework in that reduce() is not working.

Nenad Vracar Over a year ago

Reduce is pure javascript function.

zer00ne · Accepted Answer · 2016-07-03 12:44:01Z

2

You can use a combo of filter and indexOf:

function arrayUniq(arr) {
    return arr.filter(function(ele, pos) {
        return arr.indexOf(ele) == pos;
    });
}
var array1 =  
['{"STU":"Study1","SUB":"Subject1","EXL":"Yes"}','{"STU":"Study1","SUB":"Subject1","EXL":"Yes"}','{"STU":"Study2","SUB":"Subject1","EXL":"Yes"}','{"STU":"Study3","SUB":"Subject1","EXL":"Yes"}','{"STU":"Study1","SUB":"Subject1","EXL":"Yes"}','{"STU":"Study3","SUB":"Subject1","EXL":"Yes"}','{"STU":"Study3","SUB":"Subject1","EXL":"Yes"}','{"STU":"Study2","SUB":"Subject1","EXL":"Yes"}'];

var unique = arrayUniq(array1);

console.log(unique);

edited Jul 3, 2016 at 12:44

answered Jul 3, 2016 at 12:33

zer00ne

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Comments

Oz Lodriguez · Accepted Answer · 2016-07-03 19:41:12Z

Best to do it without side-effects and just using Reduce. Also keep it readable for your colleagues as well. I find I use this code snippet as a pure function a lot recently. I hope it helps you as well. Bin: https://jsbin.com/bajavucowa/edit?js,console

    var arr = [{STU: "Study1", SUB: "Subject1", EXL: "Yes"},
    {STU: "Study1", SUB: "Subject1", EXL: "Yes"},
    {STU: "Study2", SUB: "Subject1", EXL: "Yes"},
    {STU: "Study3", SUB: "Subject1", EXL: "Yes"},
    {STU: "Study1", SUB: "Subject1", EXL: "Yes"},
    {STU: "Study3", SUB: "Subject1", EXL: "Yes"},
    {STU: "Study3", SUB: "Subject1", EXL: "Yes"},
    {STU: "Study2", SUB: "Subject1", EXL: "Yes"}]
    
    
    var reducer = function(acc, next) {
      if (!acc[next.STU]) {
        acc[next.STU] = 1;
      } else {
        acc[next.STU] = acc[next.STU] + 1;
      }
      return acc;
    };
    
    var result = arr.reduce(reducer, {});

    console.log(result)

Rust in Peace · Accepted Answer · 2016-07-04 03:03:50Z

2

You can do it like this :

var array = [{STU: "Study1", SUB: "Subject1", EXL: "Yes"},
{STU: "Study1", SUB: "Subject1", EXL: "Yes"},
{STU: "Study2", SUB: "Subject1", EXL: "Yes"},
{STU: "Study3", SUB: "Subject1", EXL: "Yes"},
{STU: "Study1", SUB: "Subject1", EXL: "Yes"},
{STU: "Study3", SUB: "Subject1", EXL: "Yes"},
{STU: "Study3", SUB: "Subject1", EXL: "Yes"},
{STU: "Study2", SUB: "Subject1", EXL: "Yes"}];


function count() {
    var result = {};

    for(var i = 0; i < array.length; ++i){
        for(var el in array[i]){
          if(result[array[i][el]] !== undefined)
            result[array[i][el]] += 1;
         else
            result[array[i][el]] = 1;
      }
    }

    return result;
}

The jsfiddle is here : https://jsfiddle.net/1pfgjaf5/3/

edited Jul 4, 2016 at 3:03

answered Jul 3, 2016 at 12:35

Rust in Peace

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Comments

Mahmal Sami · Accepted Answer · 2016-07-03 12:39:20Z

Not the most efficient way, buy easy to understand: You store a "hash" of your values in an object every time you found a new value.

var tab = [ {STU: "Study1", SUB: "Subject1", EXL: "Yes"},{STU: "Study1", SUB: "Subject1", EXL: "Yes"},{STU: "Study2", SUB: "Subject1", EXL: "Yes"},{STU: "Study3", SUB: "Subject1", EXL: "Yes"},{STU: "Study1", SUB: "Subject1", EXL: "Yes"},{STU: "Study3", SUB: "Subject1", EXL: "Yes"},{STU: "Study3", SUB: "Subject1", EXL: "Yes"},{STU: "Study2", SUB: "Subject1", EXL: "Yes"}];


var result = {};
var kys;

for(var i=0; i < tab.length ; i++){
var concat = tab[i].STU + tab[i].SUB + tab[i].EXL;



kys = Object.keys(result);

if(kys.indexOf(concat) == -1){
window.console.log("element not found");
result[concat]=concat;

}else{
window.console.log("element found");
}
}
window.console.log(result);

https://jsfiddle.net/6q0w6fsc/

Piyush.kapoor · Accepted Answer · 2016-07-03 13:45:53Z

1

buildcount: function(store2){
   var datacount = store2.data.items;
var uniq = {}
    for(var i=0; i<datacount.length; i++){
        var x = datacount[i].data;
          x.forEach(function(obj) {
       uniq[obj.STU] = uniq[obj.STU] || 0;
    uniq[obj.STU]+=1;
    });
}
},

edited Jul 3, 2016 at 13:45

answered Jul 3, 2016 at 12:18

Piyush.kapoor

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3 Comments

David Over a year ago

sorry I am new in programming. In my code it is coming arr is undefined. may I know what is arr here.

David Over a year ago

My input is object and in object I have arrays, which I mention in code

Piyush.kapoor Over a year ago

From the question it looks like array of objects only, can you update the post with exact data

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