Using JavaScript combine Two JSON objects by matching key value and index value

Question

Ok, I've been racking my brain and trying this in a variety of methods, but I keep running into deadends. I even tried using Angular to do nested ng-repeats to filter down to the properties I needed but that was too heavy on resources.

What I'm trying to do is look up the value of "indices" for each object in the "groups" array, and find the corresponding object in the "person" array by matching the index to the 'indices' value, and then pushing that value to the corresponding object in the 'groups' array.

I'm trying to do this only in JavaScript when a response is returned from an api.

Example below:

    var obj = {
    "groups": [
        {
          "name": "GroupA",
          "indices": [
            0
          ]
        },
        {
          "name": "GroupB",
          "indices": [
            1
          ]
        },
        {
          "name": "GroupC",
          "indices": [
            2,
            3
          ]
        }
      ],
    "person": [
        {"name": "Archer"},
        {"name": "Lana"},
        {"name": "Mother"},
        {"name": "Barry"}
      ]
  };

And this is what I want the final object to look like:

 var obj = {
    "groups": [
        {
          "name": "GroupA",
          "indices": [
            0
          ],
        "person": [
          {"name": "Archer"}
          ]
        },
        {
          "name": "GroupB",
          "indices": [
            1
          ],
          "person": [
            {"name": "Lana"}
          ]
        },
        {
          "name": "GroupC",
          "indices": [
            2,
            3
          ],
          "person": [
            {"name": "Mother"},
            {"name": "Barry"}
          ]
        }
      ]
  };

Mark · Accepted Answer · 2017-11-13 02:12:31Z

2

I would use forEach for the outer loop rather than map but it's a matter of style more than substance:

 obj.groups.forEach(g => g.person = g.indices.map(i => obj.person[i]))

var obj = {
    "groups": [
        {
          "name": "GroupA",
          "indices": [0]
        },
        {
          "name": "GroupB",
          "indices": [ 1 ]
        },
        {
          "name": "GroupC",
          "indices": [2,3 ]
        }
      ],
    "person": [
        {"name": "Archer"},
        {"name": "Lana"},
        {"name": "Mother"},
        {"name": "Barry"}
      ]
  };

  obj.groups.forEach(g =>  g.person = g.indices.map(i => obj.person[i]))
  console.log(obj.groups)

answered Nov 13, 2017 at 2:12

Mark

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2 Comments

JohanP Over a year ago

This mutates the input tho. Could or could not be a problem but with map it's never a problem.

Mark Over a year ago

@JohanP Yes, it does. That's how I read the question: 'and then pushing that value to the corresponding object in the 'groups' array.'

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