Group and count values in an array

Question

I have an array with objects, like the following.

b = {
  "issues": [{
    "fields": {
      "status": {
        "id": "200",
        "name": "Backlog"
      }
    }
  }, {
    "fields": {
      "status": {
        "id": "202",
        "name": "close"
      }
    }
  }, {
    "fields": {
      "status": {
        "id": "201",
        "name": "close"
      }
    }
  }]
};

I want to count how many issues have status close, and how many have backlog. I'd like to save the count in a new array as follows.

a = [
  {Name: 'Backlog', count: 1},
  {Name: 'close', count: 2}
];

I have tried the following.

b.issues.forEach(function(i) {
  var statusName = i.fields.status.name;

  if (statusName in a.Name) {
    a.count = +1;
  } else {
    a.push({
      Name: statusName,
      count: 1
    });
  }
});

That however doesn't seem to be working. How should I implement this?

What’s a.count = + 1; supposed to achieve?

C3roe
– C3roe

2017-06-06 10:36:21 +00:00
Commented Jun 6, 2017 at 10:36 — C3roe
– C3roe, Commented Jun 6, 2017 at 10:36
Is the format of a fixed?

Andreas
– Andreas

2017-06-06 10:36:24 +00:00
Commented Jun 6, 2017 at 10:36 — Andreas
– Andreas, Commented Jun 6, 2017 at 10:36
I guess you mean +=

Rajesh Dixit
– Rajesh Dixit

2017-06-06 10:37:35 +00:00
Commented Jun 6, 2017 at 10:37 — Rajesh Dixit
– Rajesh Dixit, Commented Jun 6, 2017 at 10:37
no .. a is just a empty array in the beginning. b is fixed.

Shayuh
– Shayuh

2017-06-06 10:39:19 +00:00
Commented Jun 6, 2017 at 10:39 — Shayuh
– Shayuh, Commented Jun 6, 2017 at 10:39

Just a student · Accepted Answer · 2017-06-08 10:53:50Z

63

This is a perfect opportunity to use Array#reduce. That function will take a function that is applied to all elements of the array in order and can be used to accumulate a value. We can use it to accumulate an object with the various counts in it.

To make things easy, we track the counts in an object as simply {name: count, otherName: otherCount}. For every element, we check if we already have an entry for name. If not, create one with count 0. Otherwise, increment the count. After the reduce, we can map the array of keys, stored as keys of the object, to be in the format described in the question. See below.

var b = {
  "issues": [{
    "fields": {
      "status": {
        "id": "200",
        "name": "Backlog"
      }
    }
  }, {
    "fields": {
      "status": {
        "id": "202",
        "name": "close"
      }
    }
  }, {
    "fields": {
      "status": {
        "id": "201",
        "name": "close"
      }
    }
  }]
};

var counts = b.issues.reduce((p, c) => {
  var name = c.fields.status.name;
  if (!p.hasOwnProperty(name)) {
    p[name] = 0;
  }
  p[name]++;
  return p;
}, {});

console.log(counts);

var countsExtended = Object.keys(counts).map(k => {
  return {name: k, count: counts[k]}; });

console.log(countsExtended);

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

Notes.

Array#reduce does not modify the original array.
You can easily modify the function passed to reduce to for example not distinguish between Backlog and backlog by changing
```
var name = c.fields.status.name;
```
into
```
var name = c.fields.status.name.toLowerCase();
```
for example. More advanced functionality can also easily be implemented.

edited Jun 8, 2017 at 10:53

answered Jun 6, 2017 at 10:43

Just a student

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8 Comments

Shayuh Over a year ago

does this change the original array? I want the result in a different array to the orginal..

some Over a year ago

This is EXACTLY what reduce is supposed to be used for. No, it doesn't change the original array.

Shayuh Over a year ago

I tried your code .. (i have updated my code) but it says counts.map is not a function. Note: I did change a few things.. like remove the object keys function and changed the arrow function .. could u pls check it..

Just a student Over a year ago

Your problem is having removed Object.keys. The counts are stored in an object, while map is defined for arrays. We take the keys of the object (all names that were encountered) in an array and map that to the format you want. There is no such function directly for objects.

Just a student Over a year ago

@Y.Hewa I have rolled back your edit to keep the question clean, hope you don't mind. The issue should be resolved when you add Object.keys back. Just out of curiosity, why did you remove it?

|

Shivam Tiwari · Accepted Answer · 2017-06-06 10:55:10Z

3

Using ES6 Arrow functions you can do it with minimum syntax

var b = {
    "issues": [{
        "fields": {
            "status": {
                "id": "200",
                "name": "Backlog"
            }
        }
    }, {
        "fields": {
            "status": {
                "id": "202",
                "name": "close"
            }
        }
    }, {
        "fields": {
            "status": {
                "id": "201",
                "name": "close"
            }
        }
    }]
};

var countOfBackLog = b.issues.filter(x => {
return x.fields.status.name === "Backlog"
}).length

var countOfClose = b.issues.filter(x => {
return x.fields.status.name === "close"
}).length

a =[{Name: 'Backlog', count : countOfBackLog}, {Name: 'close', count : countOfClose}]

More about arrow functions here

answered Jun 6, 2017 at 10:55

Shivam Tiwari

3553 silver badges11 bronze badges

2 Comments

Alexandre Over a year ago

Actually you could do: b.issues.filter(({fields:{status:{name}}}) => name === "Backlog").length

RushabhG Over a year ago

This method wont work when we don't know the property name or there are too many property names.

Ronak Patel · Accepted Answer · 2017-06-06 10:47:23Z

1

You can write like this. It is dynamic.

var a = {}; 
for(var key in b["issues"]){ 
    if(!a.hasOwnProperty(b["issues"][key].fields.status.name)){
     a[b["issues"][key].fields.status.name] = 1;
    }else{
     a[b["issues"][key].fields.status.name] = a[b["issues"][key].fields.status.name]+1;
    }
}
var c = [];
for(var key1 in a){
   c.push({
   name  : key1,
   count : a[key1]
   });
}

answered Jun 6, 2017 at 10:47

Ronak Patel

6716 silver badges19 bronze badges

Comments

Sotiris Kiritsis · Accepted Answer · 2017-06-06 10:47:38Z

0

Something like this should do the trick. Simply iterate over your data, keep 2 counters with the number of each type of issue, and create the data format you want in the end. Try it live on jsfiddle.

var b = {
    "issues": [{
        "fields": {
            "status": {
                "id": "200",
                "name": "Backlog"
            }
        }
    }, {
        "fields": {
            "status": {
                "id": "202",
                "name": "close"
            }
        }
    }, {
        "fields": {
            "status": {
                "id": "201",
                "name": "close"
            }
        }
    }]
};

var data = [];
for(var issue of b.issues){
    var entryFound = false;
    var tempObj = {
        name: issue.fields.status.name,
        count: 1
    };

    for(var item of data){
        if(item.name === tempObj.name){
        item.count++;
        entryFound = true;
        break;
      }
    }

    if(!entryFound){
        data.push(tempObj);
    }
}
console.log(data);

edited Jun 6, 2017 at 10:47

answered Jun 6, 2017 at 10:40

Sotiris Kiritsis

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2 Comments

Shayuh Over a year ago

The thing is if there are around 10 statuses i would have to write if conditions for all of them.. is there a way to get the current status and check with the array like how ive tried to do .. ?

Sotiris Kiritsis Over a year ago

@Y.Hewa Check my updated answer. This should cover your case. You can iterate over your input and if you find it already in your list simply increase its number count by one, if not simply push it as a new item to your data array.

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