How to get number of arrays in a JSON object

Question

Below is my JSON. I want to get number and name of array(s) in this object. This is dynamically created so I don't know about its number and name(s). Here are 2 Arrays in this example, named Table and Table1.

"{
      "Table": [
        {
          "Day": "Jan",
          "Counts": 20,
          "SrNo": 1,
          "Title": "test2",
          "ProfilePic": "/Image1.jpg" 
        },
        {
          "Day": "Feb",
          "Counts": 10,
          "SrNo": 2,        
          "Title": "test2",
          "ProfilePic": "/Image1.jpg"          
        }
    ],
 "Table1": [
    {
      "Day": "01",
      "Counts": 5,
      "SrNo": 1,       
      "Title": "test3",
      "ProfilePic": "/Image2.jpg"
     },
     {
      "Day": "02",
      "Counts": 9,
      "SrNo": 2,        
      "Title": "test3",
      "ProfilePic": "/Image2.jpg",        
     }
   ]
 }"

Is it guaranteed that the arrays will only be on the first "level", and not in nested objects? — Phillip, Jun 21 '17 at 12:19
thanks for the answers, i my case i need to json.stringify i.e, Object.keys(JSON.parse(obj)).length; — Sunil Chaudhary, Jun 21 '17 at 12:24
Possible duplicate of [Get total number of items on Json object?](https://stackoverflow.com/questions/13782698/get-total-number-of-items-on-json-object) — cнŝdk, Jun 21 '17 at 12:26

score 10 · Accepted Answer · edited Jun 21 '17 at 12:36

10

Try below mentioned code,

Object.keys(jsonObject).length;

Also refer... : Get total number of items on Json object?

To get all the names :

var keys = Object.keys(jsonObject); // this will return root level title ["Table" , "Table1"]

edited Jun 21 '17 at 12:36

Vivek Doshi

56,649
12
110
122

answered Jun 21 '17 at 12:19

Binary Brackets

494
1
4
12

can we get names as well? – Sunil Chaudhary Jun 21 '17 at 12:25
To get names, just remove the `.length` part. You will now have an array of the keys :) – Phillip Jun 21 '17 at 12:25
@SunilChaudhary , var keys = Object.keys(jsonObject); // to get titles – Vivek Doshi Jun 21 '17 at 12:32
Note that this will only work if the object contains only arrays. – cнŝdk Jun 21 '17 at 12:32
if there is no array, will it return 0? – Sunil Chaudhary Jun 21 '17 at 12:33
1

@SunilChaudhary , no this is for json object , so don't worry – Binary Brackets Jun 21 '17 at 12:33

score 4 · Answer 2 · answered Jun 21 '17 at 12:20

Assuming that every property in the object contains an array, you can just count the number of properties using Object.keys, like this:

var arrayCount = Object.keys(obj).length;

Alternatively, if you actually want to determine the type of the property, in case there some other types in the object, you would need to loop through and check each property individually, which could be done using filter() like this:

var obj = {
  "Table": [{
      "Day": "Jan",
      "Counts": 20,
      "SrNo": 1,
      "Title": "test2",
      "ProfilePic": "/Image1.jpg"
    },
    {
      "Day": "Feb",
      "Counts": 10,
      "SrNo": 2,
      "Title": "test2",
      "ProfilePic": "/Image1.jpg"
    }
  ],
  "Table1": [{
      "Day": "01",
      "Counts": 5,
      "SrNo": 1,
      "Title": "test3",
      "ProfilePic": "/Image2.jpg"
    },
    {
      "Day": "02",
      "Counts": 9,
      "SrNo": 2,
      "Title": "test3",
      "ProfilePic": "/Image2.jpg",
    }
  ],
  'NotArray1': 'foo', // < not an array
  'isArray': false // < not an array
}

var arrayCount = Object.keys(obj).filter(function(key) {
  return obj[key].constructor === Array;
}).length;
console.log(arrayCount);

Yosvel Quintero · Answer 3 · 2017-06-21T12:53:06.800

You can use Array.prototype.reduce() in order to return the total of all the object property values that are valid array:

var obj = {
    "Table": [{
      "Day": "Jan",
      "Counts": 20,
      "SrNo": 1,
      "Title": "test2",
      "ProfilePic": "/Image1.jpg"
    }, {
      "Day": "Feb",
      "Counts": 10,
      "SrNo": 2,
      "Title": "test2",
      "ProfilePic": "/Image1.jpg"
    }],
    "Table1": [{
        "Day": "01",
        "Counts": 5,
        "SrNo": 1,
        "Title": "test3",
        "ProfilePic": "/Image2.jpg"
      }, {
        "Day": "02",
        "Counts": 9,
        "SrNo": 2,
        "Title": "test3",
        "ProfilePic": "/Image2.jpg"
      }
    ],
    "Table2": false
  },
  arrayCount = Object.keys(obj).reduce(function (acc, val) {
    return Array.isArray(obj[val]) ? ++acc : acc;
  }, 0);

console.log(arrayCount);

score 0 · Answer 4 · answered Dec 19 '18 at 18:30

0

In a modern browser, to count arrays in a object

Object.keys(obj).filter((e) => Array.isArray(obj[e])).length

answered Dec 19 '18 at 18:30

varatharajan

229
2
15

How to get number of arrays in a JSON object

4 Answers4