Build a map using values of multiple objects in an array javascript

Question

I need to build a map "A" from an existing array of objects. However the key value pairs on Map A are from the values of existing Object keys "id" and "cap".

Is it possible to read the values of 2 keys and store as an object

  var items =  [{
                "id": 1,
                "name": "Primary",
                "cap": [{
                        "id": "1",
                        "name": "1s"
                    }, {
                        "id": "2",
                        "name": "T2s"
                    }]
                },{
                "id": 2,
                "name": "Secondary",
                "cap": [{
                        "id": "1",
                        "name": "1s"
                    }, {
                        "id": "2",
                        "name": "T2s"
                    }
                ]
            }]

My map needs to be like this

          { "1" : [{
                        "id": "1",
                        "name": "1s"
                    }, {
                        "id": "2",
                        "name": "T2s"
                    }],
              "2" : [{
                        "id": "1",
                        "name": "1s"
                    }, {
                        "id": "2",
                        "name": "T2s"
                    }]
 }

Pankaj Shukla · Accepted Answer · 2017-05-23 22:20:53Z

2

Use Array#reduce to achieve the results like below:

var items = [{
  "id": 1,
  "name": "Primary",
  "cap": [{
    "id": "1",
    "name": "1s"
  }, {
    "id": "2",
    "name": "T2s"
  }]
}, {
  "id": 2,
  "name": "Secondary",
  "cap": [{
    "id": "1",
    "name": "1s"
  }, {
    "id": "2",
    "name": "T2s"
  }]
}];

var ans = items.reduce(function(v, i) {
  v[i.id] = i.cap;
  return v;
}, {});

console.log(ans);

edited May 23, 2017 at 22:20

answered May 23, 2017 at 22:15

Pankaj Shukla

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Comments

varbrad · Accepted Answer · 2017-05-23 22:16:39Z

1

You can do this using a simple loop on the original array, and defining a new key: value pair into the object.

// Create the map
var map = {}
// For every 'item' within the 'items' array
items.forEach(item => {
    // Map the item ID to the item.cap array
    map[item.id] = item.cap
}

var items = [{
  "id": 1,
  "name": "Primary",
  "cap": [{
    "id": "1",
    "name": "1s"
  }, {
    "id": "2",
    "name": "T2s"
  }]
}, {
  "id": 2,
  "name": "Secondary",
  "cap": [{
    "id": "1",
    "name": "1s"
  }, {
    "id": "2",
    "name": "T2s"
  }]
}]

var map = {}
items.forEach(item => {
  map[item.id] = item.cap
})

console.log(map)

answered May 23, 2017 at 22:16

varbrad

4743 silver badges12 bronze badges

Comments

Rohìt Jíndal · Accepted Answer · 2017-05-24 04:56:27Z

Using ES6 Array.from() method.

 var items =  [{
                "id": 1,
                "name": "Primary",
                "cap": [{
                        "id": "1",
                        "name": "1s"
                    }, {
                        "id": "2",
                        "name": "T2s"
                    }]
                },{
                "id": 2,
                "name": "Secondary",
                "cap": [{
                        "id": "1",
                        "name": "1s"
                    }, {
                        "id": "2",
                        "name": "T2s"
                    }
                ]
            }];

var obj = {};
var res = Array.from(items, x => obj[x.id] = x.cap);

console.log(obj);

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