Using map function in javascript

Question

My json response structure:

[
    {
        "id": 14,
        "groupname": "Angular",
        "createdAt": "2017-12-15T15:06:39.000Z",
        "updatedAt": "2017-12-15T15:06:39.000Z",
        "contactgroups": [
            {
                "id": 1,
                "contact": {
                    "id": 20,
                    "gsm": "123456789"
                }
            },
            {
                "id": 2,
                "contact": {
                    "id": 21,
                    "gsm": "987654321"
                }
            }
        ]
    },
    {
        "id": 15,
        "groupname": "React",
        "createdAt": "2017-12-15T15:06:45.000Z",
        "updatedAt": "2017-12-15T15:06:45.000Z",
        "contactgroups": [
            {
                "id": 3,
                "contact": {
                    "id": 21,
                    "gsm": "987654321"
                }
            }
        ]
    },
    {
        "id": 16,
        "groupname": "Vue",
        "createdAt": "2017-12-15T15:06:51.000Z",
        "updatedAt": "2017-12-15T15:06:51.000Z",
        "contactgroups": []
    },
    {
        "id": 17,
        "groupname": "NodeJs",
        "createdAt": "2017-12-17T16:07:38.000Z",
        "updatedAt": "2017-12-17T16:07:38.000Z",
        "contactgroups": []
    },
    {
        "id": 18,
        "groupname": "RxJS",
        "createdAt": "2017-12-21T05:50:50.000Z",
        "updatedAt": "2017-12-21T05:50:50.000Z",
        "contactgroups": []
    }
]

i have two objects inside contactgroups array, so i need to return contactsCount as 2,

if i have one object inside contactgroups i need to return contactsCount as 1, is it possible to do with map method in Javascript?

I want final output like

[
    {
        "id": 14,
        "groupname": "Angular",
        "createdAt": "2017-12-15T15:06:39.000Z",
        "updatedAt": "2017-12-15T15:06:39.000Z",
        "contactsCount: 2,
        "contactgroups": [
            {
                "id": 1,
                "contact": {
                    "id": 20,
                    "gsm": "123456789"
                }
            },
            {
                "id": 2,
                "contact": {
                    "id": 21,
                    "gsm": "987654321"
                }
            }
        ]
    },
    {
        "id": 15,
        "groupname": "React",
        "createdAt": "2017-12-15T15:06:45.000Z",
        "updatedAt": "2017-12-15T15:06:45.000Z",
        "contactsCount: 1,
        "contactgroups": [
            {
                "id": 3,
                "contact": {
                    "id": 21,
                    "gsm": "987654321"
                }
            }
        ]
    },
    {
        "id": 16,
        "groupname": "Vue",
        "createdAt": "2017-12-15T15:06:51.000Z",
        "updatedAt": "2017-12-15T15:06:51.000Z",
        "contactsCount: 0,
        "contactgroups": []
    },
    {
        "id": 17,
        "groupname": "NodeJs",
        "createdAt": "2017-12-17T16:07:38.000Z",
        "updatedAt": "2017-12-17T16:07:38.000Z",
        "contactsCount: 0,
        "contactgroups": []
    },
    {
        "id": 18,
        "groupname": "RxJS",
        "createdAt": "2017-12-21T05:50:50.000Z",
        "updatedAt": "2017-12-21T05:50:50.000Z",
        "contactsCount: 0,
        "contactgroups": []
    }
]

see now i have contactsCount inside my final output.

This is my api code:

exports.getNewGroupForProfsms = (req, res) => {
    Group.findAll({
        include: [{
            model: ContactGroup,
            attributes: ['id'],
            include: [{
                model: Contact,
                attributes: ['id', 'gsm']
            }]
        }],
    }).then(data => {
        // i am getting json here// how to do map here?
        return res.status(200).send(data);
    }).catch(err => {
        return res.status(400).send(err.message);
    });
};

score 2 · Answer 1 · answered Dec 21 '17 at 10:15

2

Use map (or forEach)

data.map( s => ( s.contactsCount = s.contactgroups.length, s ) );

Demo

var data = [
    {
        "id": 14,
        "groupname": "Angular",
        "createdAt": "2017-12-15T15:06:39.000Z",
        "updatedAt": "2017-12-15T15:06:39.000Z",
        "contactgroups": [
            {
                "id": 1,
                "contact": {
                    "id": 20,
                    "gsm": "123456789"
                }
            },
            {
                "id": 2,
                "contact": {
                    "id": 21,
                    "gsm": "987654321"
                }
            }
        ]
    }
];

data.map( s => ( s.contactsCount = s.contactgroups.length, s ) );

console.log(data);

answered Dec 21 '17 at 10:15

gurvinder372

66,980
10
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thank you, see my updated question i want to get this in response. – Mohamed Sameer Dec 21 '17 at 10:19
Did you tried using this code at that place? You just need to replace `data` with appropriate variable or JSON path. – gurvinder372 Dec 21 '17 at 10:20
yes i dont get contactsCount. can you post full answer with my api code? it will be really helpful to me – Mohamed Sameer Dec 21 '17 at 10:23
can you share the structure of the `data` in your api code? – gurvinder372 Dec 21 '17 at 10:24
Just put this line before return statement `data = data.map( s => ( s.contactsCount = s.contactgroups.length, s ) );` – gurvinder372 Dec 21 '17 at 10:37
@gurvinder272 no i put this but still i dont get contactsCount – Mohamed Sameer Dec 21 '17 at 10:40
Can you give the output of `console.log(data);` just before *return* statement and after my statement? – gurvinder372 Dec 21 '17 at 11:01
i got contactsCount in console.log but i dont get that in response, if you post full code i will solve – Mohamed Sameer Dec 21 '17 at 11:14
That is a different problem altogether and is not relevant to your original question. Check this link on how to get value from an asynchronous call https://stackoverflow.com/questions/6847697/how-to-return-value-from-an-asynchronous-callback-function – gurvinder372 Dec 21 '17 at 11:18

score 1 · Answer 2 · answered Dec 21 '17 at 10:14

1

You can map the array, and use Object#assign to return a new object with the count:

const arr = [{"id":14,"groupname":"Angular","createdAt":"2017-12-15T15:06:39.000Z","updatedAt":"2017-12-15T15:06:39.000Z","contactgroups":[{"id":1,"contact":{"id":20,"gsm":"123456789"}},{"id":2,"contact":{"id":21,"gsm":"987654321"}}]}];

const result = arr.map((o) => Object.assign({ contactsCount: o.contactgroups.length || 0 }, o));

console.log(result);

answered Dec 21 '17 at 10:14

Ori Drori

183,571
29
224
209

thank you, see my updated question i want to get this in response. – Mohamed Sameer Dec 21 '17 at 10:19

Ben Aston · Answer 3 · 2017-12-21T10:42:25.000

1

// ...    
.then((data) => 
    res.status(200).send(data.map((i) => 
        ((i.contactsCount = i.contactgroups.length), i))))
// ...

...but it is not clear why you want to do this, given that simply retrieving the length of the contactgroups array is trivial.

edited Dec 21 '17 at 10:42

answered Dec 21 '17 at 10:34

Ben Aston

53,718
65
205
331

This is my exact problem , https://stackoverflow.com/questions/47919818/node-js-writing-api-code-with-mysqlsequelize – Mohamed Sameer Dec 21 '17 at 10:39
i cant get answer , so i am doing like this – Mohamed Sameer Dec 21 '17 at 10:39
I added a missing parenthesis, pls try again. – Ben Aston Dec 21 '17 at 10:45
if i send request via postman still i dont get contactsCount in response, i think posting full api code will be really helpful to me :) – Mohamed Sameer Dec 21 '17 at 10:48
Check you are hitting the right endpoint and that the server has been restarted. Stick a debugger in to check the code is being run. – Ben Aston Dec 21 '17 at 10:50
i done all of this @ben, but i cant see contactsCount in response? will you post full api code? – Mohamed Sameer Dec 21 '17 at 10:52

score 0 · Answer 4 · answered Dec 21 '17 at 10:21

You can use data.map(contactgroupcount) like below.

var data =  [
    {
        "id": 14,
        "groupname": "Angular",
        "createdAt": "2017-12-15T15:06:39.000Z",
        "updatedAt": "2017-12-15T15:06:39.000Z",
        "contactgroups": [
            {
                "id": 1,
                "contact": {
                    "id": 20,
                    "gsm": "123456789"
                }
            },
            {
                "id": 2,
                "contact": {
                    "id": 21,
                    "gsm": "987654321"
                }
            }
        ]
    }
]

    function contactgroupcount(obj) {
       obj["contactsCount"] = obj.contactgroups.length;
        return obj;
    }

    data.map(contactgroupcount);

score 0 · Accepted Answer · answered Dec 21 '17 at 11:28

Finally this one worked for me:

exports.getNewGroupForProfsms = (req, res) => {
  Group.findAll({
    include: [{
      model: ContactGroup,
      attributes: ['id'],
      include: [{
        model: Contact,
        attributes: ['id', 'gsm']
      }]
    }],
  }).then(data => {
    // change happen here
    return res.status(200).send(data.map((x) => {
      // assign contactsCount to each row
      return Object.assign({
        contactsCount: x.contactgroups.length,
      }, x.toJSON()) // update toJSON have a try
    }));
  }).catch(err => {
    return res.status(400).send(err.message);
  });
};

Using map function in javascript

5 Answers5

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