Loop through json and fetch specific values in nodejs

Question

I have a scenario where I am trying to parse through this below json and get all the value of key "name" and key "id" , which I would further store in a variable or array.

  [
      {
        "metadata": {
          "id": "vvvvvvvvvvvvv",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app1",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
      },
        {
        "metadata": {
          "id": "vvvvvvvvvvccc",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app2",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
      },
        {
        "metadata": {
          "id": "vvvvvvvvvvddd",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app3",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
      },
        {
        "metadata": {
          "id": "vvvvvvvvvveee",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app4",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
      },
        {
        "metadata": {
          "id": "vvvvvvvvvvfff",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app5",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
    }
    ]

What I have tried till now( after this not sure how to proceed as this itself provides wrong result)

 const dJSON = require('dirty-json');

 const jsn = dJSON.parse(get_all)
 console.log(JSON.stringify(jsn));
 jsonData = JSON.stringify(jsn)
 console.log(jsonData.length) //this returns wrong value

for(var i = 0; i < jsonData.length; i++){
    for(key in jsonData[i].entity){
      if(jsonData[i].entity[key] == "name"){
          return console.log(key);
          }
      }
}

This doesn't returns the expected output. Can someone advice here as I am new to nodejs & javascript on how can I extract result like this

expected o/p :

{ 
  "app1"   :  "vvvvvvvvvvvvv", 
  "app2"   :  "vvvvvvvvvvccc",
  "app3"   :  "vvvvvvvvvvddd",
  "app4"   :  "vvvvvvvvvveee",
  "app5"   :  "vvvvvvvvvvfff" 
}

will the metadata key and entity key always be the same

Nicolas
– Nicolas

2019-10-15 16:36:27 +00:00
Commented Oct 15, 2019 at 16:36 — Nicolas
– Nicolas, Commented Oct 15, 2019 at 16:36
@Nicolas yes indeed

Thomas
– Thomas

2019-10-15 17:47:30 +00:00
Commented Oct 15, 2019 at 17:47 — Thomas
– Thomas, Commented Oct 15, 2019 at 17:47

Dan Starns · Accepted Answer · 2019-10-15 17:02:44Z

3

Here I use JSON.parse so I can use the Array.map method on the data, I use Object destructuring in the callback passed to map to pull values metadata.id and entity.name into the scope of the function. I then return a single object with entity.name as a key and metadata.id as the value. The return value from map is a new array, therefore I can use Array.reduce to transform the array into a different data structure. On each iteration of reduce the parameter current will be the individual object that was returned out of each iteration of map. Because Object.keys(current) will always be of length 1 I can use destructuring to pull the only key name out & use key/name to populate the return object.

const json = `[
    {
      "metadata": {
        "id": "vvvvvvvvvvvvv",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app1",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
    },
      {
      "metadata": {
        "id": "vvvvvvvvvvccc",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app2",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
    },
      {
      "metadata": {
        "id": "vvvvvvvvvvddd",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app3",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
    },
      {
      "metadata": {
        "id": "vvvvvvvvvveee",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app4",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
    },
      {
      "metadata": {
        "id": "vvvvvvvvvvfff",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app5",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
  }
  ]`;

const result = JSON.parse(json)
    .map(({ metadata: { id }, entity: { name } }) => {
        return { [name]: id };
    })
    .reduce((prev, current) => {
        const [name] = Object.keys(current);

        prev[name] = current[name];

        return prev;
    }, {});

console.log(result);

edited Oct 15, 2019 at 17:02

answered Oct 15, 2019 at 16:40

Dan Starns

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8 Comments

Nicolas Over a year ago

Hi, could you add a little bit more information about your answer ? Providing just code does not help.

Thomas Over a year ago

your code returns this result { app1: undefined, app2: undefined, 'app3': undefined, app4: undefined, app5: undefined }

Dan Starns Over a year ago

@Thomas are you sure, the code snippet is working fine.

Dan Starns Over a year ago

@Nicolas please see explanation

AussieJoe Over a year ago

@Thomas you need to update your question with the JSON that has the quotes. Double check your JSON, because its there in your data and not in your question.

|

Nicolas · Accepted Answer · 2019-10-15 16:40:47Z

welcome to stackoverflow ! You only need to loop through your Json once, and then get the metadata.id and the entity.name of each element :

let json = [
      {
        "metadata": {
          "id": "vvvvvvvvvvvvv",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app1",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
      },
        {
        "metadata": {
          "id": "vvvvvvvvvvccc",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app2",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
      },
        {
        "metadata": {
          "id": "vvvvvvvvvvddd",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app3",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
      },
        {
        "metadata": {
          "id": "vvvvvvvvvveee",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app4",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
      },
        {
        "metadata": {
          "id": "vvvvvvvvvvfff",
          "url": "cccccccccccccc",
          "created_at": "2019-09-06T08:40:41Z",
          "updated_at": "2019-09-06T13:25:46Z"
        },
        "entity": {
          "name": "app5",
          "b_enabled": false,
          "d_url": "xxxxxs"
        }
    }
    ]
    
  
    let output = {};
    
    // we parse each element of the json array
    for(let i = 0; i < json.length; i ++ ) {
      // we get the current element.
      let currentElement = json[i];
      // here, we are using the name of the entity as the key and the id of the metadata as the value
      output[currentElement.entity.name] = currentElement.metadata.id;
    }
    
    console.log(output);

sampie777 · Accepted Answer · 2019-10-15 16:49:25Z

0

You can use a simple forEach() function to iterate over your array. You can use the current iteration item to fill another object, like you've requested in your question.

So first you can create a object to store the filtered results in:

output = {}

Next, you can iterate over the array and fill your output object:

your_array.forEach(item => {output[item.entity.name] = item.metadata.id})

This will fill up the output object with the key-value pairs.

So what it exactly does, is that for each item in your_array, it will execute the (lambda) function {output[item.entity.name] = item.metadata.id}, where item is the current iteration item.

Total code:

var output = {};
your_array.forEach(item => {output[item.entity.name] = item.metadata.id});

// output will now be: 
//  { 
//    "app1"   :  "vvvvvvvvvvvvv", 
//    "app2"   :  "vvvvvvvvvvccc",
//    "app3"   :  "vvvvvvvvvvddd",
//    "app4"   :  "vvvvvvvvvveee",
//    "app5"   :  "vvvvvvvvvvfff" 
//  }

answered Oct 15, 2019 at 16:49

sampie777

1437 bronze badges

2 Comments

Thomas Over a year ago

It gives following error Error: TypeError: jsonData.forEach is not a function

sampie777 Over a year ago

@thomas, That is because your jsonData is a string, not an array (because you used JSON.stringify earlier. Use your variable jsn instead of jsonData.

Ayushi Keshri · Accepted Answer · 2019-10-15 17:27:51Z

0

var arr=[
    {
      "metadata": {
        "id": "vvvvvvvvvvvvv",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app1",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
    },
      {
      "metadata": {
        "id": "vvvvvvvvvvccc",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app2",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
    },
      {
      "metadata": {
        "id": "vvvvvvvvvvddd",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app3",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
    },
      {
      "metadata": {
        "id": "vvvvvvvvvveee",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app4",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
    },
      {
      "metadata": {
        "id": "vvvvvvvvvvfff",
        "url": "cccccccccccccc",
        "created_at": "2019-09-06T08:40:41Z",
        "updated_at": "2019-09-06T13:25:46Z"
      },
      "entity": {
        "name": "app5",
        "b_enabled": false,
        "d_url": "xxxxxs"
      }
  }
  ]
  
  var myMap =new Map();
 
  arr.forEach((element,index)=>{
    var a= arr[index]
    var id='';
    var name='';
    
   var c= Object.keys(a).map(item=>{
     // console.log(item)
       if(item=="metadata"){
       id=a[item]["id"]
       
       }
      else{
         name=a[item]["name"]
         
         }
        }
   )
  myMap[name]=id;
      
     
  })
  console.log(myMap)

Well not the best and optimized solution (i am too new to js) but this solves your problem statement. I am just trying to get the each element of an array which is object and then within each object trying to get the keys of the individual and storing it in variable and then pushing it to the map for desired output. P.s. use you input as arr.

edited Oct 15, 2019 at 17:27

answered Oct 15, 2019 at 17:02

Ayushi Keshri

6907 silver badges18 bronze badges

5 Comments

AussieJoe Over a year ago

Did you run your code snippet? It produces an error.

Ayushi Keshri Over a year ago

in visual studio it is showing the output. Let me debug it

AussieJoe Over a year ago

You haven't included the JSON in the example code snippet. You might want to update your code snippet or remove it since it doesn't work.

Thomas Over a year ago

@AyushiKeshri i am not sure but when i try this , it gives me Error: TypeError: arr.forEach is not a function

Ayushi Keshri Over a year ago

@Thomas it is working code in vsc , codepen and here .So might be you are doing something wrong.Also common mistake the input is array if you are taking it an object then object dont have for each loop in that case refer: stackoverflow.com/questions/31096596/…

gabriel.hayes · Accepted Answer · 2019-10-15 16:40:36Z

-1

  const jsObj = JSON.parse(json);
  const result = jsObj.map(entry => ({name: entry.entity.name, id: entry.metadata.id}));
  const objResult = {};
  result.forEach(entry => {
    objResult[entry.name] = entry.id;
  });
  console.log(objResult);

Output:

{ app1: 'vvvvvvvvvvvvv',
  app2: 'vvvvvvvvvvccc',
  app3: 'vvvvvvvvvvddd',
  app4: 'vvvvvvvvvveee',
  app5: 'vvvvvvvvvvfff' }

edited Oct 15, 2019 at 16:40

answered Oct 15, 2019 at 16:36

gabriel.hayes

2,31312 silver badges15 bronze badges

1 Comment

Nicolas Over a year ago

Hi, could you add more information about your answer ?

Srinivas · Accepted Answer · 2019-10-15 16:41:04Z

-1

In output

key = entity.name

val = metadata.id

of each doc

The approach is simple. Intilize an empty object. Put key, val in empty object.

var result = {}
jsonData.forEach(x => {
   result[x.entity.name]= x.metadata.id
})

https://jsfiddle.net/v8w2L1oa/

edited Oct 15, 2019 at 16:41

answered Oct 15, 2019 at 16:36

Srinivas

3743 silver badges23 bronze badges

3 Comments

Nicolas Over a year ago

Hi, could you add more information about your answer ?

Dan Starns Over a year ago

this returns an array, the question ask for an object to be returned

Srinivas Over a year ago

@DanStarns Hey, can you check js filddle once. You will get clear answer.

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